Aeolian processes over gravel beds: Field wind tunnel simulation and its application atop the Mogao Grottoes, China

NASA Astrophysics Data System (ADS)

Zhang, Weimin; Tan, Lihai; Zhang, Guobin; Qiu, Fei; Zhan, Hongtao

2014-12-01

The aeolian processes of erosion, transport and deposition are threatening the Mogao Grottoes, a world culture heritage site. A field wind tunnel experiment was conducted atop the Mogao Grottoes using weighing sensors to quantify aeolian processes over protective gravel beds. Results reveal that aeolian erosion and deposition over gravel beds are basically influenced by gravel coverage and wind speed. Erosion is a main aeolian process over gravel beds and its strength level is mainly determined by gravel coverage: strong (<30%), medium (30-50%) and slight (>50%). Aeolian deposition only occurs when gravel coverage is equal to or greater than 30% and wind speeds are between 8 and 12 m s-1, and this process continues until the occurrence of the equilibrium coverage. In addition, the change in conditions of external sand supply affects the transition between aeolian deposition and erosion over gravel beds, and the quantity of sand transport at the height of 0-24 mm is an important indicator of aeolian deposition and erosion over gravel beds. Our results also demonstrate that making the best use of wind regime atop the Mogao Grottoes and constructing an artificial gobi surface in staggered arrays, with 30% coverage and 30-mm-high gravels and in 40 mm spacing can trap westerly invading sand flow and enable the stronger easterly wind to return the deposited sand on the gravel surface back to the Mingsha Mountain so as to minimize the damage of the blown sand flux to the Mogao Grottoes.

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.

Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA

USGS Publications Warehouse

Draut, Amy E.

2012-01-01

Connectivity between fluvial and aeolian sedimentary systems plays an important role in the physical and biological environment of dryland regions. This study examines the coupling between fluvial sand deposits and aeolian dune fields in bedrock canyons of the arid to semiarid Colorado River corridor, southwestern USA. By quantifying significant differences between aeolian landscapes with and without modern fluvial sediment sources, this work demonstrates for the first time that the flow- and sediment-limiting effects of dam operations affect sedimentary processes and ecosystems in aeolian landscapes above the fluvial high water line. Dune fields decoupled from fluvial sand supply have more ground cover (biologic crust and vegetation) and less aeolian sand transport than do dune fields that remain coupled to modern fluvial sand supply. The proportion of active aeolian sand area also is substantially lower in a heavily regulated river reach (Marble–Grand Canyon, Arizona) than in a much less regulated reach with otherwise similar environmental conditions (Cataract Canyon, Utah). The interconnections shown here among river flow and sediment, aeolian sand transport, and biologic communities in aeolian dunes demonstrate a newly recognized means by which anthropogenic influence alters dryland environments. Because fluvial–aeolian coupling is common globally, it is likely that similar sediment-transport connectivity and interaction with upland ecosystems are important in other dryland regions to a greater degree than has been recognized previously.

Aeolian Sediment Transport Pathways and Aerodynamics at Troughs on Mars

NASA Technical Reports Server (NTRS)

Bourke, Mary C.; Bullard, Joanna E.; Barnouin-Jha, Olivier S.

2004-01-01

Interaction between wind regimes and topography can give rise to complex suites of aeolian landforms. This paper considers aeolian sediment associated wit11 troughs on Mars and identifies a wider range of deposit types than has previously been documented. These include wind streaks, falling dunes, "lateral" dunes, barchan dunes, linear dunes, transverse ridges, sand ramps, climbing dunes, sand streamers, and sand patches. The sediment incorporated into these deposits is supplied by wind streaks and ambient Planitia sources as well as originating within the trough itself, notably from the trough walls and floor. There is also transmission of sediment between dneTsh. e flow dynamics which account for the distribution of aeolian sediment have been modeled using two-dimensional computational fluid dynamics. The model predicts flow separation on the upwind side of the trough followed by reattachment and acceleration at the downwind margin. The inferred patterns of sediment transport compare well with the distribution of aeolian forms. Model data indicate an increase of wind velocity by approx. 30 % at the downwind trough margin. This suggests that the threshold wind speed necessary for sand mobilization on Mars will be more freqentmlye t in these inclined locations.

Aeolian sands and buried soils in the Mecklenburg Lake District, NE Germany: Holocene land-use history and pedo-geomorphic response

NASA Astrophysics Data System (ADS)

Küster, Mathias; Fülling, Alexander; Kaiser, Knut; Ulrich, Jens

2014-04-01

The present study is a pedo-geomorphic approach to reconstructing Holocene aeolian sand dynamics in the Mecklenburg Lake District (NE Germany). Stratigraphical, sedimentological and soil research supplemented by morphogenetic interpretations of the genesis of dunes and aeolian sands are discussed. A complex Late Holocene aeolian stratigraphy within a drift sand area was developed at the shore of Lake Müritz. The results were confirmed using palynological records, archaeological data and regional history. Accelerated aeolian activity was triggered by the intensification of settlement and land-use activities during the 13th and in the 15th to 16th century AD. After a period of stability beginning with population decline during the ‘Thirty Years War' and continuing through the 18th century, a final aeolian phase due to the establishment of glassworks was identified during the 19th century AD. We assume a direct link between Holocene aeolian dynamics and human activities. Prehistoric Holocene drift sands on terrestrial sites have not been documented in the Mecklenburg Lake District so far. This might be explained either by erosion and incorporation of older aeolian sediments during younger aeolian phases and/or a lower regional land-use intensity in older periods of the Holocene. The investigated drift sands are stratigraphically and sedimentologically characterised by a high degree of heterogeneity, reflecting the spatial and temporal variability of Holocene human impact.

Turbulent Flow and Sand Dune Dynamics: Identifying Controls on Aeolian Sediment Transport

NASA Astrophysics Data System (ADS)

Weaver, C. M.; Wiggs, G.

2007-12-01

Sediment transport models are founded on cubic power relationships between the transport rate and time averaged flow parameters. These models have achieved limited success and recent aeolian and fluvial research has focused on the modelling and measurement of sediment transport by temporally varying flow conditions. Studies have recognised turbulence as a driving force in sediment transport and have highlighted the importance of coherent flow structures in sediment transport systems. However, the exact mechanisms are still unclear. Furthermore, research in the fluvial environment has identified the significance of turbulent structures for bedform morphology and spacing. However, equivalent research in the aeolian domain is absent. This paper reports the findings of research carried out to characterise the importance of turbulent flow parameters in aeolian sediment transport and determine how turbulent energy and turbulent structures change in response to dune morphology. The relative importance of mean and turbulent wind parameters on aeolian sediment flux was examined in the Skeleton Coast, Namibia. Measurements of wind velocity (using sonic anemometers) and sand transport (using grain impact sensors) at a sampling frequency of 10 Hz were made across a flat surface and along transects on a 9 m high barchan dune. Mean wind parameters and mass sand flux were measured using cup anemometers and wedge-shaped sand traps respectively. Vertical profile data from the sonic anemometers were used to compute turbulence and turbulent stress (Reynolds stress; instantaneous horizontal and vertical fluctuations; coherent flow structures) and their relationship with respect to sand transport and evolving dune morphology. On the flat surface time-averaged parameters generally fail to characterise sand transport dynamics, particularly as the averaging interval is reduced. However, horizontal wind speed correlates well with sand transport even with short averaging times. Quadrant

Synthesis on Quaternary aeolian research in the unglaciated eastern United States

USGS Publications Warehouse

Markewich, Helaine Walsh; Litwin, Ronald J.; Wysocki, Douglas A.; Pavich, Milan J.

2015-01-01

Late-middle and late Pleistocene, and Holocene, inland aeolian sand and loess blanket >90,000 km2 of the unglaciated eastern United States of America (USA). Deposits are most extensive in the Lower Mississippi Valley (LMV) and Atlantic Coastal Plain (ACP), areas presently lacking significant aeolian activity. They provide evidence of paleoclimate intervals when wind erosion and deposition were dominant land-altering processes. This study synthesizes available data for aeolian sand deposits in the LMV, the Eastern Gulf Coastal Plain (EGCP) and the ACP, and loess deposits in the Middle Atlantic Coastal Plain (MACP). Data indicate: (a) the most recent major aeolian activity occurred in response to and coincident with growth and decay of the Laurentide Ice Sheet (LIS); (b) by ∼40 ka, aeolian processes greatly influenced landscape evolution in all three regions; (c) aeolian activity peaked in OIS2; (d) OIS3 and OIS2 aeolian records are in regional agreement with paleoecological records; and (e) limited aeolian activity occurred in the Holocene (EGCP and ACP). Paleoclimate and atmospheric-circulation models (PCMs/ACMs) for the last glacial maximum (LGM) show westerly winter winds for the unglaciated eastern USA, but do not resolve documented W and SW winds in the SEACP and WNW and N winds in the MACP. The minimum areal extent of aeolian deposits in the EGCP and ACP is ∼10,000 km2. For the LMV, it is >80,000 km2. Based on these estimates, published PCMs/ACMs likely underrepresent the areal extent of LGM aeolian activity, as well as the extent and complexity of climatic changes during this interval.

Synthesis on Quaternary aeolian research in the unglaciated eastern United States

NASA Astrophysics Data System (ADS)

Markewich, Helaine W.; Litwin, Ronald J.; Wysocki, Douglas A.; Pavich, Milan J.

2015-06-01

Late-middle and late Pleistocene, and Holocene, inland aeolian sand and loess blanket >90,000 km2 of the unglaciated eastern United States of America (USA). Deposits are most extensive in the Lower Mississippi Valley (LMV) and Atlantic Coastal Plain (ACP), areas presently lacking significant aeolian activity. They provide evidence of paleoclimate intervals when wind erosion and deposition were dominant land-altering processes. This study synthesizes available data for aeolian sand deposits in the LMV, the Eastern Gulf Coastal Plain (EGCP) and the ACP, and loess deposits in the Middle Atlantic Coastal Plain (MACP). Data indicate: (a) the most recent major aeolian activity occurred in response to and coincident with growth and decay of the Laurentide Ice Sheet (LIS); (b) by ∼40 ka, aeolian processes greatly influenced landscape evolution in all three regions; (c) aeolian activity peaked in OIS2; (d) OIS3 and OIS2 aeolian records are in regional agreement with paleoecological records; and (e) limited aeolian activity occurred in the Holocene (EGCP and ACP). Paleoclimate and atmospheric-circulation models (PCMs/ACMs) for the last glacial maximum (LGM) show westerly winter winds for the unglaciated eastern USA, but do not resolve documented W and SW winds in the SEACP and WNW and N winds in the MACP. The minimum areal extent of aeolian deposits in the EGCP and ACP is ∼10,000 km2. For the LMV, it is >80,000 km2. Based on these estimates, published PCMs/ACMs likely underrepresent the areal extent of LGM aeolian activity, as well as the extent and complexity of climatic changes during this interval.

2009 weather and aeolian sand-transport data from the Colorado River corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Draut, Amy E.; Sondossi, Hoda A.; Dealy, Timothy P.; Hazel, Joseph E.; Fairley, Helen C.; Brown, Christopher R.

2010-01-01

This report presents measurements of weather parameters and aeolian sand transport made in 2009 near selected archeological sites in the Colorado River corridor through Grand Canyon, Ariz. The quantitative methods and data discussed here form a basis for monitoring ecosystem processes that affect archeological-site stability. Combined with forthcoming work to evaluate landscape evolution at nearby archeological sites, these data can be used to document the relation between physical processes, including weather and aeolian sand transport, and their effects on the physical integrity of archeological sites. Data collected in 2009 reveal event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Broad seasonal changes in aeolian sediment flux are also apparent at most study sites. Differences in weather patterns between 2008 and 2009 included an earlier spring windy season, greater spring precipitation even though 2009 annual rainfall totals were in general substantially lower than in 2008, and earlier onset of the reduced diurnal barometric-pressure fluctuations commonly associated with summer monsoon conditions. Weather patterns in middle to late 2009 were apparently affected by a transition of the ENSO cycle from a neutral phase to the El Ni?o phase. The continuation of monitoring that began in 2007, and installation of additional equipment at several new sites in early 2008, allowed evaluation of the effects of the March 2008 high-flow experiment (HFE) on aeolian sand transport. As reported earlier, at 2 of the 9 sites studied, spring and summer winds in 2008 reworked the HFE sandbars to form new aeolian dunes, where sand moved inland toward larger, well-established dune fields. Observations in 2009 showed that farther inland migration of the dune at one of those two sites is likely inhibited by vegetation. At the other location, the new aeolian dune form was found to have moved 10 m inland toward older, well

Optically stimulated luminescence dating of aeolian sand in the otindag dune field and holocene climate change

USGS Publications Warehouse

Zhou, Y.L.; Lu, H.Y.; Mason, J.; Miao, X.D.; Swinehart, J.; Goble, R.

2008-01-01

The dune system in Otindag sand field of northern China is sensitive to climate change, where effective moisture and related vegetation cover play a controlling role for dune activity and stability. Therefore, aeolian deposits may be an archive of past environmental changes, possibly at the millennial scale, but previous studies on this topic have rarely been reported. In this study, thirty-five optically stimulated luminescence (OSL) ages of ten representative sand-paleosol profiles in Otindag sand field are obtained, and these ages provide a relatively complete and well-dated chronology for wet and dry variations in Holocene. The results indicate that widespread dune mobilization occurred from 9.9 to 8.2 ka, suggesting a dry early Holocene climate. The dunes were mainly stabilized between 8.0 and 2.7 ka, implying a relatively wet climate, although there were short-term penetrations of dune activity during this wet period. After ???2.3 ka, the region became dry again, as inferred from widespread dune activity. The "8.2 ka" cold event and the Little Ice Age climatic deterioration are detected on the basis of the dune records and OSL ages. During the Medieval Warm Period and the Sui-Tang Warm Period (570-770 AD), climate in Otindag sand field was relatively humid and the vegetation was denser, and the sand dunes were stabilized again. These aeolian records may indicate climate changes at millennial time scale during Holocene, and these climatic changes may be the teleconnection to the climate changes elsewhere in the world. ?? Science in China Press and Springer-Verlag GmbH 2008.

Late Pleistocene and Holocene aeolian sedimentation in Gonghe Basin, northeastern Qinghai-Tibetan Plateau: Variability, processes, and climatic implications

NASA Astrophysics Data System (ADS)

Qiang, Mingrui; Jin, Yanxiang; Liu, Xingxing; Song, Lei; Li, Hao; Li, Fengshan; Chen, Fahu

2016-01-01

Although stratigraphic sequences of aeolian deposits in dryland areas have long been recognized as providing information about past environments, the exact nature of the environmental processes they reflect remains unclear. Here, we report the results of a detailed investigation of eight outcrop sections in the Gonghe Basin, northeastern Qinghai-Tibetan Plateau. Measurements of sediment grain-size and chemical composition indicate that the deposits are primarily of aeolian origin, consisting of interbedded, well-sorted sand, silty sand, loess and/or palaeosol; however, their occurrence varies from site to site. Fossil dune sands mainly occur in or close to the currently stabilized or semi-stabilized dune fields, whereas loess is distributed along the downwind marginal areas. This pattern of basin-scale differentiation was controlled mainly by spatial variability of sediment supply due to the antecedent sedimentary patterns within the basin. Together with previously-published optically stimulated luminescence (OSL) ages, 24 new OSL dates are used to elucidate the history of aeolian activity and its relationship to climatic changes. There is no apparent relationship between past dune activity and downwind loess deposits. Deposition of silty sand probably occurred during past phases of windy, dry and cold climate in the Late Pleistocene. However, climatic factors alone cannot explain the occurrence of silty sand deposition. This is because the deposition of silty sand was always preceded by episodes of fluvial deposition prior to river incision, thereby indicating the importance of an 'activated' sediment supply associated with fluvial processes. Deposition of well-sorted sand occurred episodically, not only during the Late Pleistocene, but also during the early- to mid-Holocene. Vegetation conditions, controlled either by the occurrence of intervals of moisture deficit during the Late Pleistocene or by changes in the balance between precipitation and

2007 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Draut, Amy E.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.

2009-01-01

Weather data constitute an integral part of ecosystem monitoring in the Colorado River corridor and are particularly valuable for understanding processes of landscape change that contribute to the stability of archeological sites. Data collected in 2007 are reported from nine weather stations in the Colorado River corridor through Grand Canyon, Ariz. The stations were deployed in February and March 2007 to measure wind speed and direction, rainfall, air temperature, relative humidity, and barometric pressure. Sand traps near each weather station collect windblown sand, from which daily aeolian sand-transport rates are calculated. The data reported here were collected as part of an ongoing study to test and evaluate methods for quantifying processes that affect the physical integrity of archeological sites along the river corridor; as such, these data can be used to identify rainfall events capable of causing gully incision and to predict likely transport pathways for aeolian sand, two landscape processes integral to the preservation of archeological sites. Weather data also have widespread applications to other studies of physical, cultural, and biological resources in Grand Canyon. Aeolian sand-transport data reported here, collected in the year before the March 2008 High-Flow Experiment (HFE) at Glen Canyon Dam, represent baseline data against which the effects of the 2008 HFE on windblown sand will be compared in future reports.

Gully annealing by fluvially-sourced Aeolian sand: remote sensing investigations of connectivity along the Fluvial-Aeolian-hillslope continuum on the Colorado River

USGS Publications Warehouse

Sankey, Joel B.; East, Amy E.; Collins, Brian D.; Caster, Joshua J.

2015-01-01

Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term, land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This work investigates gully annealing by aeolian sediment, along the Colorado River downstream of Glen Canyon Dam in Glen, Marble, and Grand Canyons, Arizona, USA (Figure 1). In this segment of the Colorado River, gully erosion potentially affects the stability and preservation of archaeological sites that are located within valley margins. Gully erosion occurs as a function of ephemeral, rainfall-induced overland flow associated with intense episodes of seasonal precipitation. Measurements of sediment transport and topographic change have demonstrated that fluvial sand in some locations is transported inland and upslope by aeolian processes to areas affected by gully erosion, and aeolian sediment activity can be locally effective at counteracting gully erosion (Draut, 2012; Collins and others, 2009, 2012; Sankey and Draut, 2014). The degree to which specific locations are affected by upslope wind redistribution of sand from active channel sandbars to higher elevation valley margins is termed “connectivity”. Connectivity is controlled spatially throughout the river by (1) the presence of upwind sources of fluvial sand within the contemporary active river channel (e.g., sandbars), and (2) bio-physical barriers that include vegetation and topography that might impede aeolian sediment transport. The primary hypothesis of this work is that high degrees of connectivity lead to less gullying potential.

Clear cutting (10-13th century) and deep stable economy (18-19th century) as responsible interventions for sand drifting and plaggic deposition in cultural landscapes on aeolian sands (SE-Netherlands).

NASA Astrophysics Data System (ADS)

van Mourik, Jan; Vera, Hein; Wallinga, Jakob

2013-04-01

The landscape in extensive areas in SE-Netherlands is underlain by coversand, deposited during the Late Glacial of the Weichselian. In the Preboreal, aeolian processes reduced soil formation. From the Preboreal to the Atlantic a deciduous climax forest developed. The geomorphology was a coversand landscape, composed of ridges (umbric podzols), coversand plains (gleyic podzols), coversand depressions (histic podzols) and small valleys (gleysols). The area was used by hunting people during the Late Paleolithic and Mesolithic. During the Bronze and Iron Ages the area was populated by people, living from forest grazing, shifting cultivation and trade. The natural deciduous forest gradually degraded into Calluna heath. The deforestation accelerated the soil acidification and affected the hydrology, which is reflected in drying out of ridges and wetting of depressions, promoting the development of histic podzols and even histosols. Aeolian erosion was during this period restricted to local, small scale sand drifting, related to natural hazards as forest fires and hurricanes and shifting cultivation. Sustainable crop productivity on chemically poor sandy substrates required application of organic fertilizers, composed of a mixture of organic litter and animal manure with a very low mineral compound, produced in shallow stables. At least since 1000 AD, heath management was regulated by a series of rules that aimed to protect the valuable heat lands against degradation. During the 11th, 12th and 13th centuries there was an increasing demand for wood and clear cutting transformed the majority of the forests in driftsand landscapes. The most important market was formed by the very wealthy Flemish cities. The exposed soil surface was subjected to wind erosion and sand drifting which endangered the Calluna heath, arable land and even farmhouses. As a consequence, umbric podzols, the natural climax soil under deciduous forests on coversand, degraded into larger scale driftsand

Modeling grain size variations of aeolian gypsum deposits at White Sands, New Mexico, using AVIRIS imagery

USGS Publications Warehouse

Ghrefat, H.A.; Goodell, P.C.; Hubbard, B.E.; Langford, R.P.; Aldouri, R.E.

2007-01-01

Visible and Near-Infrared (VNIR) through Short Wavelength Infrared (SWIR) (0.4-2.5????m) AVIRIS data, along with laboratory spectral measurements and analyses of field samples, were used to characterize grain size variations in aeolian gypsum deposits across barchan-transverse, parabolic, and barchan dunes at White Sands, New Mexico, USA. All field samples contained a mineralogy of ?????100% gypsum. In order to document grain size variations at White Sands, surficial gypsum samples were collected along three Transects parallel to the prevailing downwind direction. Grain size analyses were carried out on the samples by sieving them into seven size fractions ranging from 45 to 621????m, which were subjected to spectral measurements. Absorption band depths of the size fractions were determined after applying an automated continuum-removal procedure to each spectrum. Then, the relationship between absorption band depth and gypsum size fraction was established using a linear regression. Three software processing steps were carried out to measure the grain size variations of gypsum in the Dune Area using AVIRIS data. AVIRIS mapping results, field work and laboratory analysis all show that the interdune areas have lower absorption band depth values and consist of finer grained gypsum deposits. In contrast, the dune crest areas have higher absorption band depth values and consist of coarser grained gypsum deposits. Based on laboratory estimates, a representative barchan-transverse dune (Transect 1) has a mean grain size of 1.16 ??{symbol} (449????m). The error bar results show that the error ranges from - 50 to + 50????m. Mean grain size for a representative parabolic dune (Transect 2) is 1.51 ??{symbol} (352????m), and 1.52 ??{symbol} (347????m) for a representative barchan dune (Transect 3). T-test results confirm that there are differences in the grain size distributions between barchan and parabolic dunes and between interdune and dune crest areas. The t-test results

Natural and human controls of the Holocene evolution of the beach, aeolian sand and dunes of Caesarea (Israel)

NASA Astrophysics Data System (ADS)

Roskin, J.; Sivan, D.; Shtienberg, G.; Roskin, E.; Porat, N.; Bookman, R.

2015-12-01

The study focuses on the Holocene appearance, chronology and drivers of beach sand deposition and inland aeolian sand transport around the Roman-Byzantine ruins of Caesarea, Israel. Beach sand, sand sheets, nebkha, linear and transverse dunes as well as parabolic and transverse interdunes along two transects were sampled in the current study down to their substrate. Sixteen new optically stimulated luminescence ages cluster at ∼5.9-3.3 ka, ∼1.2-1.1 ka (800-900 AD) and ∼190-120 years ago (1825-1895 AD) indicating times of middle and late Holocene sand sheet depositions and historical dune stabilization. The first age cluster indicates that beach sand accumulated when rates of global sea level rise declined around 6-5 ka. Until ∼4 ka sand sheets encroached up to 2.5 km inland. Historical and archaeological evidence points to sand mobilization since the first century AD. Sand sheets dating to 1.2-1.1 ka, coevally found throughout the dunefield represent sand stabilization due to vegetation reestablishment attributed to gradual and fluctuating decline in human activity from the middle Early Islamic period until the 10th century. Historical and chronological evidence of the existence of transverse and coppice dunes from the 19th century suggest that dunes only formed in the last few centuries. The study illustrates the initial role of natural processes, in this case decline in global sea level rise and the primary and later role of fluctuating human activity upon coastal sand mobility. The study distinguishes between sand sheets and dunes and portrays them as sensors of environmental changes.

Aeolian stratigraphy describes ice-age paleoenvironments in unglaciated Arctic Alaska

NASA Astrophysics Data System (ADS)

Gaglioti, Benjamin V.; Mann, Daniel H.; Groves, Pamela; Kunz, Michael L.; Farquharson, Louise M.; Reanier, Richard E.; Jones, Benjamin M.; Wooller, Matthew J.

2018-02-01

Terrestrial paleoenvironmental records with high dating resolution extending into the last ice age are rare from the western Arctic. Such records can test the synchronicity and extent of ice-age climatic events and define how Arctic landscapes respond to rapid climate changes. Here we describe the stratigraphy and sedimentology of a yedoma deposit in Arctic Alaska (the Carter Section) dating to between 37,000 and 9000 calibrated radiocarbon years BP (37-9 ka) and containing detailed records of loess and sand-sheet sedimentation, soil development, carbon storage, and permafrost dynamics. Alternation between sand-sheet and loess deposition provides a proxy for the extent and activity of the Ikpikpuk Sand Sea (ISS), a large dune field located immediately upwind. Warm, moist interstadial times (ca. 37, 36.3-32.5, and 15-13 ka) triggered floodplain aggradation, permafrost thaw, reduced loess deposition, increased vegetation cover, and rapid soil development accompanied by enhanced carbon storage. During the Last Glacial Maximum (LGM, ca. 28-18 ka), rapid loess deposition took place on a landscape where vegetation was sparse and non-woody. The most intense aeolian activity occurred after the LGM between ca. 18 and 15 ka when sand sheets fringing the ISS expanded over the site, possibly in response to increasingly droughty conditions as summers warmed and active layers deepened. With the exception of this lagged LGM response, the record of aeolian activity at the Carter Section correlates with other paleoenvironmental records from unglaciated Siberia and Alaska. Overall, rapid shifts in geomorphology, soils, vegetation, and permafrost portray an ice-age landscape where, in contrast to the Holocene, environmental change was chronic and dominated by aeolian processes.

Recent seasonal variations in arid landscape cover and aeolian sand mobility, Navajo Nation, southwestern U.S.

USGS Publications Warehouse

Draut, Amy E.; Redsteer, Margaret Hiza; Amoroso, Lee; Giosan, Liviu; Fuller, Dorian Q.; Nicoll, Kathleen; Flad, Rowan K.; Clift, Peter D.

2013-01-01

The socioeconomic impacts of climate change pose problems not only in devel- oping countries but also to residents of arid lands in the United States among marginalized societies with limited economic means. In the Navajo Nation, warming temperatures and recent drought have increased aeolian sediment mobility such that large, migrating sand dunes affect grazing lands, housing, and road access. Dust derived from this region also affects albedo and longevity of the Rocky Mountains snowpack, located downwind. We present initial results from a study that monitors sand transport and vegetation within a 0.2 km2 site in the Navajo lands, measuring the effects of drought on landscape stability since 2009. Sand mobility decreased substantially as 1 year with near-normal monsoon rainfall (2010) somewhat abated a decade-long drought, temporarily doubling vegetation cover. Vegetation that grew during 2010, with adequate rain, died off rapidly during dry conditions in 2011. Short-term increases in rainfall that promote annual, but not perennial, plant growth will not improve landscape stability in the long term. Climate projections suggest that a warmer, drier climate and potentially enhanced sediment supply from ephem- eral washes will further increase aeolian sand transport and dune activity, worsening the present challenges to people living in this region. Connections among climate, vegetation, and aeolian sediment erodibility in this region are highly relevant to other areas of the world with similar environmental problems.

Facies architecture and stratigraphic evolution of aeolian dune and interdune deposits, Permian Caldeirão Member (Santa Brígida Formation), Brazil

NASA Astrophysics Data System (ADS)

Jones, Fábio Herbert; Scherer, Claiton Marlon dos Santos; Kuchle, Juliano

2016-05-01

The Permian Caldeirão Member (Santa Brígida Formation), located in the Tucano Central Basin, northeast region of Brazil, is characterized by a sandstone succession of aeolian origin that comprises the preserved deposits of dunes and interdunes. Grainflow and translatent wind-ripple strata, and frequent presence of reactivation surface, compose the cross-bedding of crescent aeolian dune deposits. The aeolian cross-strata show a mean dip toward the ENE. In places, interlayered with dune cross-beds, occur interdune units composed of facies indicative of dry, damp and wet condition of the substrate, suggesting spatial and/or temporal variations in the moisture content of the interdune accumulation surface. The presence of NNW current ripple cross-lamination in wet interdune areas indicates streamflows confined to interdune corridors and oriented perpendicular to aeolian transport direction. Lenses of damp and wet interdune strata exhibit mainly interdigitated and transitional relationships with the toe-sets of overlying aeolian dune units in sections parallel to aeolian transport, indicating that dune migration was contemporaneous with accumulation in adjacent interdunes. Lateral variations in the preserved thickness of the interdune units and the associated rare occurrence of abrupt and erosive contacts between interdune and overlying dune sets, suggest temporal variations in the angle of dune and interdune climb that may be related to high-frequency changes in water table position. Four stratigraphic intervals in the Caldeirão Member can be identified, two intervals showing cross-bedding of aeolian dunes without wet interdune areas and two intervals exhibiting aeolian dunes separated by wet interdune areas, marking the transition between dry aeolian systems (Intervals I and III) and wet aeolian systems (Intervals II and IV). The temporal alternations between dry and wet aeolian systems reflect changes in the availability of dry sand and/or the rate in the water

Sand ramps as palaeoenvironmental archives: Integrating general principles and regional contexts through reanalysis of the Klipkraal Sands, South Africa

NASA Astrophysics Data System (ADS)

Rowell, Alexandra L. K.; Thomas, David S. G.; Bailey, Richard M.; Holmes, Peter J.

2018-06-01

Sand ramps occur on a continuum of topographically-controlled landforms, ranging from purely aeolian features (climbing/falling dunes) to talus cones and alluvial fans. Sand ramps have been identified as potentially important palaeoenvironmental archives in dryland regions that possess relatively few Quaternary proxy records. Their utility however requires not only good age control of depositional phases but clear identification of process regimes, determined through morphological and sedimentological analyses, with several recent studies indicating the complexities of palaeoenvironmental interpretations and the controls of ramp development (Bateman et al., 2012; Rowell et al., 2018). Klipkraal Sands is a sand ramp on the north-eastern margin of the semi-arid Karoo that has been important for inferences of the extent of southern African Late Quaternary aeolian activity (Thomas et al., 2002). We reanalyse this feature, in the light of both its significance and other recent studies that have inferred extensive southern African LGM aeolian activity (Telfer et al., 2012, 2014). New sedimentological data and twelve OSL dates indicate the Klipkraal Sands formed episodically between 100-0.14 ka, rather than accumulating rapidly, while sedimentological data question the aeolian affinities of the bulk of the feature. Therefore, Klipkraal is reinterpreted as showing no particular affinity to the LGM, with sediments locally sourced with a significant colluvial component. Only the upper historical sediments can be clearly interpreted as aeolian deposits. A complex interplay of processes is suggested, for which a meaningful palaeoenvironmental interpretation cannot be easily defined. This implies that the local geomorphic processes and controls operating on sand ramps need to be established before they can be fully utilised as palaeoenvironmental archives, with implications for their interpretation worldwide.

Aeolian Environments of Iceland

NASA Astrophysics Data System (ADS)

Arnalds, Olafur; Olafsson, Haraldur; Dagsson Waldhauserová, Pavla

2017-04-01

Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland's location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since the time of the settlement of Iceland in the late ninth century. There are about 135 dust events per annum, ranging from minor storms to >300,000 t of dust emitted in single storms. Dust can be generated from all the major sandy areas of Iceland; however the amount of finer particles that become dust varies with the surfaces. There are areas that produce more dust by far compared to the general sandy deserts; they have therefore been termed "dust plume areas" or "dust hot-spots". They are characterized by repeated charging of fine sediments with a relatively high proportion of finer (silty) materials which, upon repeated wind erosion become sorted downwind from the sources with loss of silt (dust) and an increasing saltation component (sand). Dust production is on the order of 30-40 million tons annually, some travelling over 1000 km and deposited on land and sea. Dust deposited on deserts tends to be re-suspended during subsequent storms. High PM10 concentrations occur during major dust

Controls on late Holocene drift-sand dynamics: the role of people and climate on inland aeolian activity in the Netherlands

NASA Astrophysics Data System (ADS)

Pierik, Harm Jan; Van Lanen, Rowin; Gouw-Bouman, Marjolein; Groenewoudt, Bert; Wallinga, Jakob; Hoek, Wim

2017-04-01

Holocene drift-sand activity is commonly linked directly to either population pressure (via agricultural activity) or to climate change (e.g. storminess). In the Pleistocene sand areas of the Netherlands small-scale Holocene aeolian activity occurred since the Neolithic, whereas large scale drift-sand activity started during the Middle Ages (especially after AD 1000. This last phase coincides with the intensification of farming and demographic pressure, but is also commonly associated with a colder climate and enhanced storminess. This raises the question to what extent drift-sand activity can be attributed to human activities or to natural forcing factors. In this study we compare the spatial and chronological patterns of drift-sand occurrence for four characteristic Pleistocene sand regions in the Netherlands. For this, we compiled a new supra-regional overview of dates related to drift-sand activity (14C, OSL, archaeological and historical), that we compared with existing national soil maps, historical-route networks, and vegetation and climate reconstructions. Results show a steady occurrence of aeolian activity between 1000 BC and AD 1000, interrupted by remarkable dip in aeolian activity around 2000 BP, probably caused by changing land-use practices or by lower storminess. It is evident that human pressure on the landscape was most influential on initiating sand drifting: this is supported by more frequent occurrence close to routes and the uninterrupted increase in drift-sand activity after ca AD 1000 during periods of high population density and large-scale deforestation. Once triggered by human activities, the drift-sand development was probably further enhanced several centuries later during the cold and more stormy Little Ice Age (AD 1570-1900).

Investigating the use of the dual-polarized and large incident angle of SAR data for mapping the fluvial and aeolian deposits

NASA Astrophysics Data System (ADS)

Gaber, Ahmed; Amarah, Bassam A.; Abdelfattah, Mohamed; Ali, Sarah

2017-12-01

Mapping the spatial distributions of the fluvial deposits in terms of particles size as well as imaging the near-surface features along the non-vegetated aeolian sand-sheets, provides valuable geological information. Thus this work aims at investigating the contribution of the dual-polarization SAR data in classifying and mapping the surface sediments as well as investigating the effect of the radar incident-angle on improving the images of the hidden features under the desert sand cover. For mapping the fluvial deposits, the covariance matrix ([C2]) using four dual-polarized ALOS/PALSAR-1 scenes cover the Wadi El Matulla, East Qena, Egypt were generated. This [C2] matrix was used to generate a supervised classification map with three main classes (gravel, gravel/sand and sand). The polarimetric scattering response, spectral reflectance and temperatures brightness of these 3 classes were extracted. However for the aeolian deposits investigation, two Radarsat-1 and three full-polarimetric ALOS/PALSAR-1 images, which cover the northwestern sandy part of Sinai, Egypt were calibrated, filtered, geocoded and ingested in a GIS database to image the near-surface features. The fluvial mapping results show that the values of the radar backscattered coefficient (σ°) and the degree of randomness of the obtained three classes are increasing respectively by increasing their grain size. Moreover, the large incident angle (θi = 39.7) of the Radarsat-1 image has revealed a meandering buried stream under the sand sheet of the northwestern part of Sinai. Such buried stream does not appear in the other optical, SRTM and SAR dataset. The main reason is the enhanced contrast between the low backscattered return from the revealed meandering stream and the surroundings as a result of the increased backscattering intensity, which is related to the relatively large incident angle along the undulated surface of the study area. All archaeological observations support the existence of

Abrasion resistance of muscovite in aeolian and subaqueous transport experiments

NASA Astrophysics Data System (ADS)

Anderson, Calvin J.; Struble, Alexander; Whitmore, John H.

2017-02-01

Complementary aeolian and subaqueous transport experiments showed a trend in muscovite abrasion that may be useful for identifying ancient sandstones as aeolian or subaqueous in origin. We found that our experimental aeolian processes pulverized the micas quickly, while our subaqueous processes did not. In a pair of abrasion resistance experiments conducted with micaceous quartz sand, it was found that large muscovite grains were (1) reduced by aeolian processes to less than 500 μm in just 4 days, and (2) preserved by subaqueous processes to 610 ± 90 μm even after 356 days. At 20 days of aeolian transport no loose micas could be found even under the microscope, but after a year of subaqueous transport loose muscovite grains could still be seen with the naked eye. Thus, the occurrence and character of micas in a sandstone, particularly muscovite, may be helpful in determining the ancient depositional process.

MAHLI at the Rocknest sand shadow: Science and science-enabling activities

NASA Astrophysics Data System (ADS)

Minitti, M. E.; Kah, L. C.; Yingst, R. A.; Edgett, K. S.; Anderson, R. C.; Beegle, L. W.; Carsten, J. L.; Deen, R. G.; Goetz, W.; Hardgrove, C.; Harker, D. E.; Herkenhoff, K. E.; Hurowitz, J. A.; Jandura, L.; Kennedy, M. R.; Kocurek, G.; Krezoski, G. M.; Kuhn, S. R.; Limonadi, D.; Lipkaman, L.; Madsen, M. B.; Olson, T. S.; Robinson, M. L.; Rowland, S. K.; Rubin, D. M.; Seybold, C.; Schieber, J.; Schmidt, M.; Sumner, D. Y.; Tompkins, V. V.; Van Beek, J. K.; Van Beek, T.

2013-11-01

Martian solar days 57-100, the Mars Science Laboratory Curiosity rover acquired and processed a solid (sediment) sample and analyzed its mineralogy and geochemistry with the Chemistry and Mineralogy and Sample Analysis at Mars instruments. An aeolian deposit—herein referred to as the Rocknest sand shadow—was inferred to represent a global average soil composition and selected for study to facilitate integration of analytical results with observations from earlier missions. During first-time activities, the Mars Hand Lens Imager (MAHLI) was used to support both science and engineering activities related to sample assessment, collection, and delivery. Here we report on MAHLI activities that directly supported sample analysis and provide MAHLI observations regarding the grain-scale characteristics of the Rocknest sand shadow. MAHLI imaging confirms that the Rocknest sand shadow is one of a family of bimodal aeolian accumulations on Mars—similar to the coarse-grained ripples interrogated by the Mars Exploration Rovers Spirit and Opportunity—in which a surface veneer of coarse-grained sediment stabilizes predominantly fine-grained sediment of the deposit interior. The similarity in grain size distribution of these geographically disparate deposits support the widespread occurrence of bimodal aeolian transport on Mars. We suggest that preservation of bimodal aeolian deposits may be characteristic of regions of active deflation, where winnowing of the fine-sediment fraction results in a relatively low sediment load and a preferential increase in the coarse-grained fraction of the sediment load. The compositional similarity of Martian aeolian deposits supports the potential for global redistribution of fine-grained components, combined with potential local contributions.

Cross-bedding set thickness and stratigraphic architecture of aeolian systems: An example from the Upper Permian Pirambóia Formation (Paraná Basin), southern Brazil

NASA Astrophysics Data System (ADS)

Dias, Kayo Delorenzo Nardi; Scherer, Claiton M. S.

2008-05-01

The Pirambóia Formation comprises an unconformity-bounded aeolian succession essentially composed of three facies associations: aeolian sand sheet, aeolian dune and interdune facies associations. The lower portion of the Pirambóia Formation is characterised by aeolian sand sheet deposits, which are overlain by aeolian dune and interdune strata, hence pointing to an overall increase in sand availability within the paleoerg. The dune and interdune successions can be further subdivided into two distinct stratigraphic intervals in terms of their mean set thickness. Intervals 1 and 2 display mean set thicknesses of 2.9 and 6.19 m, respectively. This increase in the mean set thickness reflects an increase of the angle of climb and/or dune size. In addition to improve the stratigraphic subdivision, the recognition and correlation of intervals with distinct mean set thicknesses provides a tool for reconstructing aeolian erg architecture from drill cores.

Declines in a ground-dwelling arthropod community during an invasion by Sahara mustard (Brassica tournefortii) in aeolian sand habitats

Treesearch

Heather L. Hulton VanTassel; Anne M. Hansen; Cameron W. Barrows; Quresh Latif; Margaret W. Simon; Kurt E. Anderson

2014-01-01

Sahara Mustard (Brassica tournefortii; hereafter mustard), an exotic plant species, has invaded habitats throughout the arid southwestern United States. Mustard has reached high densities across aeolian sand habitats of southwestern deserts, including five distinct sand habitats in the eastern Coachella Valley, California. We examined trends in ground-dwelling...

Increasing aeolian dust deposition to snowpacks in the Rocky Mountains inferred from snowpack, wet deposition, and aerosol chemistry

USGS Publications Warehouse

Clow, David W.; Williams, Mark W.; Schuster, Paul F.

2016-01-01

Mountain snowpacks are a vital natural resource for ∼1.5 billion people in the northern Hemisphere, helping to meet human and ecological demand for water in excess of that provided by summer rain. Springtime warming and aeolian dust deposition accelerate snowmelt, increasing the risk of water shortages during late summer, when demand is greatest. While climate networks provide data that can be used to evaluate the effect of warming on snowpack resources, there are no established regional networks for monitoring aeolian dust deposition to snow. In this study, we test the hypothesis that chemistry of snow, wet deposition, and aerosols can be used as a surrogate for dust deposition to snow. We then analyze spatial patterns and temporal trends in inferred springtime dust deposition to snow across the Rocky Mountains, USA, for 1993–2014. Geochemical evidence, including strong correlations (r2 ≥ 0.94) between Ca2+, alkalinity, and dust concentrations in snow deposited during dust events, indicate that carbonate minerals in dust impart a strong chemical signature that can be used to track dust deposition to snow. Spatial patterns in chemistry of snow, wet deposition, and aerosols indicate that dust deposition increases from north to south in the Rocky Mountains, and temporal trends indicate that winter/spring dust deposition increased by 81% in the southern Rockies during 1993–2014. Using a multivariate modeling approach, we determined that increases in dust deposition and decreases in springtime snowfall combined to accelerate snowmelt timing in the southern Rockies by approximately 7–18 days between 1993 and 2014. Previous studies have shown that aeolian dust emissions may have doubled globally during the 20th century, possibly due to drought and land-use change. Climate projections for increased aridity in the southwestern U.S., northern Africa, and other mid-latitude regions of the northern Hemisphere suggest that aeolian dust emissions may continue to

Aeolian sedimentary processes at the Bagnold Dunes, Mars: Implications for modern dune dynamics and sedimentary structures in the aeolian stratigraphic record of Mars

NASA Astrophysics Data System (ADS)

Ewing, Ryan C.; Bridges, Nathan T.; Sullivan, Rob; Lapotre, Mathieu G. A.; Fischer, Woodward W.; Lamb, Mike P.; Rubin, David M.; Lewis, Kevin W.; Gupta, Sanjeev

2016-04-01

Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under Martian conditions. In-situ observations of sand dunes (informally called the Bagnold Dunes) by Curiosity Rover in Gale Crater, Mars provide the first opportunity to make observations of dunes from the grain-to-dune scale thereby filling the gap in knowledge between theory and orbital observations and refining our understanding of the martian aeolian stratigraphic record. We use the suite of cameras on Curiosity, including Navigation Camera (Navcam), Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI), to make observations of the Bagnold Dunes. Measurements of sedimentary structures are made where stereo images are available. Observations indicate that structures generated by gravity-driven processes on the dune lee slopes, such as grainflow and grainfall, are similar to the suite of aeolian sedimentary structures observed on Earth and should be present and recognizable in Mars' aeolian stratigraphic record. Structures formed by traction-driven processes deviate significantly from those found on Earth. The dune hosts centimeter-scale wind ripples and large, meter-scale ripples, which are not found on Earth. The large ripples migrate across the depositional, lee slopes of the dune, which implies that these structures should be present in Mars' stratigraphic record and may appear similar to compound-dune stratification.The Mars Science Laboratory Curiosity Rover Team is acknowledged for their support of this work.

Optical Dating of Holocene Dune Sands in the Ferris Dune Field, Wyoming

NASA Astrophysics Data System (ADS)

Stokes, Stephen; Gaylord, David R.

1993-05-01

Optical 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.

An Old-Growth Definition for Sand Pine Forests

Treesearch

Kenneth W. Outcalt

1997-01-01

Sand pine scrub, Society of American Foresters cover type 69 (Eyre 1980), grows on deep, droughty, infertile sands of marine and aeolian origin. Water and wind formed these features as sea levels fluctuated during past glacial and interglacial periods (Kurz 1942, Laessle 1958, Brooks 1972). Because of washing and sorting during transport and deposition, soil parent...

Aeolian sand transport over complex intertidal bar-trough beach topography

NASA Astrophysics Data System (ADS)

Anthony, Edward J.; Ruz, Marie-Hélène; Vanhée, Stéphane

2009-04-01

Aeolian sand transport on macrotidal beaches with complex intertidal bar-trough topography (ridge-and-runnel beaches) was assessed from experiments in northern France that involved measurements of wind speed, saltation, surface moisture contents, and rates of sand trapping across surveyed portions of the upper beach profile. Beaches exhibiting intertidal bars and troughs are much more complex, topographically, than simple reflective or dissipative beaches. Furthermore, the intertidal bar-trough morphology commonly exhibits strong cross-shore variations in the moisture contents of the beach surface and in patterns of bedform development. The results of four 30-minute experiments, conducted along topographically surveyed portions of the upper beach-dune toe profile, show that troughs act as extremely efficient sand interceptors, because of their permanently saturated state, which also inhibits sand mobilisation. Troughs, thus, limit or segment the dry fetch during conditions of intermittent saltation. Flow lines, inferred from the wind profiles, suggest that complex interactions at the boundary layer are generated by the bar-trough topography. Troughs systematically appear to be characterised by air expansion, while bar faces generate ramp wind acceleration for onshore winds, and sometimes immediate downwind deceleration for offshore winds. These effects may also contribute to cross-shore variations in the rates of sand trapping. Finally, a simple conceptual model of effective fetch development, integrating the effects of the spring-neap tidal range and of gross bar-trough morphological variability over time, is proposed for bar-trough beaches. The model highlights the key theme of fetch segmentation induced by cross-shore differentiation in the moisture contents of the beach surface hinged on the complex topography of multiple bars and troughs.

Sediment grain-size characteristics and relevant correlations to the aeolian environment in China's eastern desert region.

PubMed

Zhang, Chunlai; Shen, Yaping; Li, Qing; Jia, Wenru; Li, Jiao; Wang, Xuesong

2018-06-15

To identify characteristics of aeolian activity and the aeolian environment in China's eastern desert region, this study collected surface sediment samples from the main desert and sandy lands in this region: the Hobq Desert and the Mu Us, Otindag, Horqin, and Hulunbuir sandy lands. We analyzed the grain-size characteristics and their relationships to three key environmental indicators: drift potential, the dune mobility index, and vegetation cover. The main sediment components are fine to medium sands, with poor (Hulunbuir) to moderate (all other areas) sorting, of unimodal to bimodal distribution. This suggests that improved sorting is accomplished by the loss of both relatively coarser and finer grains. Since 2000, China's eastern desert region has generally experienced low wind energy environmental conditions, resulting in decreased dune activity. In the Hobq Desert, however, the dry climate and sparse vegetation, in conjunction with the most widely distributed mobile dune area in the eastern desert region, have led to frequent and intense aeolian activity, including wind erosion, sand transport, and deposition, resulting in conditions for good sediment sorting. In the Mu Us, Otindag, and Horqin sandy lands, mosaic distribution has resulted from wind erosion-dominated and deposition-dominated aeolian environments. In the Hulunbuir Sandy Land, high precipitation, low temperatures, and steppe vegetation have resulted in well-developed soils; however, strong winds and flat terrain have created an aeolian environment dominated by wind erosion. Copyright © 2018. Published by Elsevier B.V.

Relations between rainfall–runoff-induced erosion and aeolian deposition at archaeological sites in a semi-arid dam-controlled river corridor

USGS Publications Warehouse

Collins, Brian D.; Bedford, David; Corbett, Skye C.; Fairley, Helen C.; Cronkite-Ratcliff, Collin

2016-01-01

Process dynamics in fluvial-based dryland environments are highly complex with fluvial, aeolian, and alluvial processes all contributing to landscape change. When anthropogenic activities such as dam-building affect fluvial processes, the complexity in local response can be further increased by flood- and sediment-limiting flows. Understanding these complexities is key to predicting landscape behavior in drylands and has important scientific and management implications, including for studies related to paleoclimatology, landscape ecology evolution, and archaeological site context and preservation. Here we use multi-temporal LiDAR surveys, local weather data, and geomorphological observations to identify trends in site change throughout the 446-km-long semi-arid Colorado River corridor in Grand Canyon, Arizona, USA, where archaeological site degradation related to the effects of upstream dam operation is a concern. Using several site case studies, we show the range of landscape responses that might be expected from concomitant occurrence of dam-controlled fluvial sand bar deposition, aeolian sand transport, and rainfall-induced erosion. Empirical rainfall-erosion threshold analyses coupled with a numerical rainfall–runoff–soil erosion model indicate that infiltration-excess overland flow and gullying govern large-scale (centimeter- to decimeter-scale) landscape changes, but that aeolian deposition can in some cases mitigate gully erosion. Whereas threshold analyses identify the normalized rainfall intensity (defined as the ratio of rainfall intensity to hydraulic conductivity) as the primary factor governing hydrologic-driven erosion, assessment of false positives and false negatives in the dataset highlight topographic slope as the next most important parameter governing site response. Analysis of 4+ years of high resolution (four-minute) weather data and 75+ years of low resolution (daily) climate records indicates that dryland erosion is dependent on short

Modeling surficial sand and gravel deposits

USGS Publications Warehouse

Bliss, J.D.; Page, N.J.

1994-01-01

Mineral-deposit models are an integral part of quantitative mineral-resource assessment. As the focus of mineral-deposit modeling has moved from metals to industrial minerals, procedure has been modified and may be sufficient to model surficial sand and gravel deposits. Sand and gravel models are needed to assess resource-supply analyses for planning future development and renewal of infrastructure. Successful modeling of sand and gravel deposits must address (1) deposit volumes and geometries, (2) sizes of fragments within the deposits, (3) physical characteristics of the material, and (4) chemical composition and chemical reactivity of the material. Several models of sand and gravel volumes and geometries have been prepared and suggest the following: Sand and gravel deposits in alluvial fans have a median volume of 35 million m3. Deposits in all other geologic settings have a median volume of 5.4 million m3, a median area of 120 ha, and a median thickness of 4 m. The area of a sand and gravel deposit can be predicted from volume using a regression model (log [area (ha)] =1.47+0.79 log [volume (million m3)]). In similar fashion, the volume of a sand and gravel deposit can be predicted from area using the regression (log [volume (million m3)]=-1.45+1.07 log [area (ha)]). Classifying deposits by fragment size can be done using models of the percentage of sand, gravel, and silt within deposits. A classification scheme based on fragment size is sufficiently general to be applied anywhere. ?? 1994 Oxford University Press.

Aerolian erosion, transport, and deposition of volcaniclastic sands among the shifting sand dunes, Christmas Lake Valley, Oregon: TIMS image analysis

NASA Technical Reports Server (NTRS)

Edgett, Kenneth S.; Ramsey, Michael S.; Christensen, Philip R.

1995-01-01

Remote sensing is a tool that, in the context of aeolian studies, offers a synoptic view of a dune field, sand sea, or entire desert region. Blount et al. (1990) presented one of the first studies demonstrating the power of multispectral images for interpreting the dynamic history of an aeolian sand sea. Blount's work on the Gran Desierto of Mexico used a Landsat TM scene and a linear spectral mixing model to show where different sand populations occur and along what paths these sands may have traveled before becoming incorporated into dunes. Interpretation of sand transport paths and sources in the Gran Desierto led to an improved understanding of the origin and Holocene history of the dunes. With the anticipated advent of the EOS-A platform and ASTER thermal infrared capability in 1998, it will become possible to look at continental sand seas and map sand transport paths using 8-12 mu m bands that are well-suited to tracking silicate sediments. A logical extension of Blount's work is to attempt a similar study using thermal infrared images. One such study has already begun by looking at feldspar, quartz, magnetite, and clay distributions in the Kelso Dunes of southern California. This paper describes the geology and application of TIMS image analysis of a less-well known Holocene dune field in south central Oregon using TIMS data obtained in 1991.

Sands at Gusev Crater, Mars

NASA Astrophysics Data System (ADS)

Cabrol, Nathalie A.; Herkenhoff, Kenneth; Knoll, Andrew H.; Farmer, Jack; Arvidson, Raymond; Grin, Edmond; Li, Ronxing; Fenton, Lori; Cohen, Barbara; Bell, James F.; Aileen Yingst, R.

2014-05-01

Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine-to-medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).

Sands at Gusev Crater, Mars

USGS Publications Warehouse

Cabrol, Nathalie A.; Herkenhoff, Kenneth E.; Knoll, Andrew H.; Farmer, Jack D.; Arvidson, Raymond E.; Grin, E.A.; Li, Ron; Fenton, Lori; Cohen, B.; Bell, J.F.; Yingst, R. Aileen

2014-01-01

Processes, environments, and the energy associated with the transport and deposition of sand at Gusev Crater are characterized at the microscopic scale through the comparison of statistical moments for particle size and shape distributions. Bivariate and factor analyses define distinct textural groups at 51 sites along the traverse completed by the Spirit rover as it crossed the plains and went into the Columbia Hills. Fine-to-medium sand is ubiquitous in ripples and wind drifts. Most distributions show excess fine material, consistent with a predominance of wind erosion over the last 3.8 billion years. Negative skewness at West Valley is explained by the removal of fine sand during active erosion, or alternatively, by excess accumulation of coarse sand from a local source. The coarse to very coarse sand particles of ripple armors in the basaltic plains have a unique combination of size and shape. Their distribution display significant changes in their statistical moments within the ~400 m that separate the Columbia Memorial Station from Bonneville Crater. Results are consistent with aeolian and/or impact deposition, while the elongated and rounded shape of the grains forming the ripples, as well as their direction of origin, could point to Ma'adim Vallis as a possible source. For smaller particles on the traverse, our findings confirm that aeolian processes have dominated over impact and other processes to produce sands with the observed size and shape patterns across a spectrum of geologic (e.g., ripples and plains soils) and aerographic settings (e.g., wind shadows).

The contribution of micrometeorites to the iron stocks of buried podzols, developed in Late-glacial aeolian sand deposits (Brabant, The Netherlands)

NASA Astrophysics Data System (ADS)

van Mourik, Jan; de Vet, Sebastiaan

2015-04-01

The surface geology of an extensive part of NW-Europe is dominated by coversands (Late-glacial chemical poor aeolian sand deposits). The geomorphology of coversand landscapes is dominated by ridges and planes. Podzolation is the dominant soil forming process in coversands under moderate humid climatic conditions. Umbric Podzols developed on the ridges under Quercetum-mixtum, Gleyic and Histic Podzols developed in the planes under Alnetum. Even in chemical poor coversands, iron will be released by hydrolysis from iron containing silicate minerals (such as feldspars). It is well known that the vertical iron distribution in Podzols is effected by translocation of active iron from eluvial to illuvial horizons and that iron is leaching to the aquifer. Iron stocks of Podzols, in contrasts, have not been widely studied for comparison purposes of individual soil horizons or between soils. We determined the stocks of active and immobile iron in the horizons of buried xeromorphic Podzols (soils that developed without any contact with groundwater). The results show that the total amount of iron exceeds the potential amount which can be released by hydrolysis from the parent material. Furthermore, to amount of iron that leached to the groundwater is unknown. It is evident that we must find an additional source to explain the total iron stocks in buried Podzols. It is known from analysis of ice cores that the earth atmosphere is subjected to a continuous influx of (iron rich) micrometeorites. The precipitation of micrometeorites (and other aerosols) on the earth surface is concentrated in humid climatic zones with (intensive) rain fall. We analyzed minerals, extracted from the ectorganic horizon of the Initial Podzols, developed in driftsand that stabilized around 1900 AD, overlying Palaeopodzols, buried around 1200 AD. Among blown in quartz grains, we could determine also micrometeorites, embedded in the organic skeleton of the fermentation horizon of the Initial Podzol

Adaptation to life in aeolian sand: how the sandfish lizard, Scincus scincus, prevents sand particles from entering its lungs.

PubMed

Stadler, Anna T; Vihar, Boštjan; Günther, Mathias; Huemer, Michaela; Riedl, Martin; Shamiyeh, Stephanie; Mayrhofer, Bernhard; Böhme, Wolfgang; Baumgartner, Werner

2016-11-15

The sandfish lizard, Scincus scincus (Squamata: Scincidae), spends nearly its whole life in aeolian sand and only comes to the surface for foraging, defecating and mating. It is not yet understood how the animal can respire without sand particles entering its respiratory organs when buried under thick layers of sand. In this work, we integrated biological studies, computational calculations and physical experiments to understand this phenomenon. We present a 3D model of the upper respiratory system based on a detailed histological analysis. A 3D-printed version of this model was used in combination with characteristic ventilation patterns for computational calculations and fluid mechanics experiments. By calculating the velocity field, we identified a sharp decrease in velocity in the anterior part of the nasal cavity where mucus and cilia are present. The experiments with the 3D-printed model validate the calculations: particles, if present, were found only in the same area as suggested by the calculations. We postulate that the sandfish has an aerodynamic filtering system; more specifically, that the characteristic morphology of the respiratory channel coupled with specific ventilation patterns prevent particles from entering the lungs. © 2016. Published by The Company of Biologists Ltd.

Correlation of aeolian sediment transport measured by sand traps and fluorescent tracers

NASA Astrophysics Data System (ADS)

Cabrera, Laura L.; Alonso, Ignacio

2010-03-01

Two different methods, fluorescent tracers and vertical sand traps, were simultaneously used to carry out an aeolian sediment transport study designed to test the goodness of fluorescent tracers in aeolian environments. Field experiments were performed in a nebkha field close to Famara beach at Lanzarote Island (Canary Islands, Spain) in a sector where the dunes were between 0.5 and 0.8 m height and 1-2 m wide and the vegetal cover was approximately 22%. In this dune field the sediment supply comes from Famara beach and is blown by trade winds toward the south, where the vegetation acts as natural sediment traps. Wind data were obtained by means of four Aanderaa wind speed sensors and one Aanderaa vane, all them distributed in a vertical array from 0.1 to 4 m height for 27 h. The average velocity at 1 m height during the experiment was 5.26 m s - 1 with the wind direction from the north. The tracer was under wind influence for 90 min at midday. During this period two series of sand traps (T1 and T2) N, S, E and W oriented were used. Resultant transport rates were 0.0131 and 0.0184 kg m - 1 min - 1 respectively. Tracer collection was performed with a sticky tape to sample only surface sediments. Tagged grains were visually counted under UV light. The transport rate was computed from the centroid displacement, that moved 0.875 m southwards, and the depth of the active layer considered was the size of one single grain. Taking into account these data the transport rate was 0.0072 kg m - 1 min - 1 . The discrepancy in results between both methods is related to several factors, such as the thickness of the active layer and the grain size difference between the tagged and the native material.

Insights from Askja sand sheet, Iceland, as a depositional analogue for the Bagnold Dune Field, Gale Crater, Mars.

NASA Astrophysics Data System (ADS)

Ukstins, I.; Sara, M.; Riishuus, M.; Schmidt, M. E.; Yingst, R. A.; Berger, J.

2017-12-01

Examining the compositional effect of aeolian transport and sorting processes on basaltic sands is significant for understanding the evolution of the Bagnold dune field, as well as other martian soils and sedimentary units. We use the Askja sand sheet, Iceland, as a testbed to quantify the nature of soil production and aeolian transport processes in a mafic system. Basalts from Askja and surrounding volcanic units, which can have high MgO (5-18 wt %) and high Fe2O3 (5-18 wt %), have been weathered to form mafic volcaniclastic deposits which are incorporated into a 40-km long sand sheet to the E-SE of the caldera, ranging from 10 cm to 10 m thick, and covering 240 km2. Ash and lava from the 2014-2015 Holuhraun eruption were emplaced onto the southeastern part of the sand sheet. The SW section is deflationary and defined by very fine to medium grained basaltic sand with ventifact cobbles and boulders. The central part is inflating and dominated by very fine-grained sand, relict lava fields, and small to large sand ripples (1 to 30 cm). The NE portion is also inflating but accumulation is limited to topographic depressions. Bulk chemistry of >200 sand samples are similar to Martian crust (SiO2: 48-52 wt %, MgO: 5-8 wt %, Fe2O3: 13-15 wt %). MgO concentrations vary with distance along the sand sheet, increasing by 1.5% over 10 km in the downwind direction (E, NE), then maintaining a relatively consistent concentration of 6.75 wt % over 18 km. Mean equancy of grains decreases 15 % to the E over 10 km followed by a plateau at 65 to 75 %. Material at depth tends to be of higher sphericity than material on or near the surface. Notably, MgO increases while the sphericity decreases and both data sets level off at 10 km, which suggests these two variables are related. These indicate input of material with prismoidal morphology around 10 km, and may be due to the Holuhraun eruption.

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

NASA Technical Reports Server (NTRS)

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

1999-01-01

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

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

NASA Astrophysics Data System (ADS)

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

1999-09-01

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

Quantifying the effects of European beach grass on aeolian sand transport over the last century: Bodega Marine Reserve, California

NASA Astrophysics Data System (ADS)

Cesmat, R.; Werner, S.; Smith, M. E.; Riedel, T.; Best, R.; Olyarnik, S.

2012-12-01

Introduction of European beach grass (Ammophila arenaria) to coastal dune systems of western North America induced significant changes to the transport and storage of sediment, and consequently the nesting habitat of the western snowy plover (Charadrius alexandrinus nivosus). At the Bodega Marine Reserve and Sonoma Coast State Park, Ammophila was introduced within the ~0.5 km2 dune area in the 1920's to limit the flux of sand through Bodega Harbor and agricultural land. To assess the potential impact of restoration efforts (Ammophila removal) on aeolian sediment flux, we measured sediment flux as a function of wind speeds and ground cover, and used these measurements to parameterize a spatial model for historical sand deposition Fine- to coarse-grained lithic to sub-lithic sand is delivered to the Bodega dune system from Salmon Creek beach, the down-shore terminus of a littoral system fed by the 3846 km2 Russian River catchment, several small (<100 km2) coastal catchments, and seacliff erosion. Littoral sediment traverses the 1.8 km wide dune system from NW to SE via aeolian transport. Ammophila colonization occurred initially adjacent to the shoreface, inducing deposition of a ~10 meter-high foredune and has subsequently encroached the ~0.5 km2 region between the foredune and Bodega Harbor. Comparison of historical topographic maps via raster subtraction indicates rapid construction of both the foredune and a ~15 meter-high transverse dune (Gaffney ridge) at the edge of the planted region. An average accumulation rate of ~4,000 m3/yr is indicated within the study swath by the preserved sediment volumes. Within the modern dune system, unvegetated areas exhibit 2-3 meter wavelength, ~1/2 meter amplitude mega-ripples, and the uppermost 2-10 cm consists of coarse-sand to granule-sized armor layer. In contrast, grain-sizes in vegetated areas are largely vertically homogenous. Open areas are typically 2-8 meters lower than adjacent vegetated areas, and show evidence for

Sand incursion into temperate (Lithuania) and tropical (the Bahamas) maritime vegetation: Georadar visualization of target-rich aeolian lithosomes

NASA Astrophysics Data System (ADS)

Buynevich, Ilya V.; Savarese, Michael; Curran, H. Allen; Bitinas, Albertas; Glumac, Bosiljka; Pupienis, Donatas; Kopcznski, Karen; Dobrotin, Nikita; Gnivecki, Perry; Boush, Lisa Park; Damušytė, Aldona

2017-08-01

Interaction of windblown sand with maritime vegetation, either as dune migration or episodic grain transport is a common phenomenon along many sandy coasts. Vegetation introduces antecedent surface roughness, especially when scaled to the landform height, but its role may be concealed if overwhelmed by aeolian incursion and burial. Where field observations and cores lack detail for characterizing this complex process, ground-penetrating radar (GPR) offers continuous visualization of aeolian sequences. Along the Curonian Spit, Lithuania, dune reactivation phases resulted in massive invasion of siliciclastic sand triggered by natural perturbations and land clearance. Massive (>30 m high) dunes entombed mature pine, oak, and alder stands and this process is ongoing. Mid-frequency (200 MHz) georadar surveys reveal landward-dipping lateral accretion surfaces interrupted by high-amplitude point-source anomalies produced by recently buried trees. In tropical regions, dense vegetation and potential for rapid lithification of carbonate sand results in more complex internal structures. Along the windward coast of San Salvador Island, the Bahamas, a massive dune has buried several generations of maritime scrubland, resulting in highly chaotic reflection pattern and high target density. On a nearby Little Exuma Island, numerous reentrants in aeolianites promoted formation of blowouts and incursion of windblown sand 10-25 m into a silver thatch palm forest. High-frequency (800 MHz) GPR images resolve diffractions from trunks and roots buried by > 2 m of oolitic sand. Basal refection morphology helps differentiate the irregular dune/beachrock surface from a smooth palm-frond mat. Aside from detecting and mapping buried vegetation, geophysical images capture its effect on sediment accumulation. This has the potential for differentiating its effect from other discordant structures within dunes (clasts, dissolution voids, trunk molds, burrows, and cultural remains).

Comminution of Aeolian Materials on Mars

NASA Technical Reports Server (NTRS)

Marshall, John R.

1998-01-01

The research task had a two-year performance period for the investigation of aeolian processes on Mars. Specifically, we were investigating the comminution of sand grains as individual particles, and as bulk populations. Laboratory experiment were completed for the individual particles, and results led to new theory for aeolian transport that is broadly applicable to all planetary surfaces. The theory was presented at the LPSC and the GSA in 1998 and 1997 respectively. Essentially, the new theory postulates that aeolian transport is dependent upon two motion thresholds- an aerodynamic threshold and a bed-dilatancy threshold.

Aeolian deposition change in the Peruvian central continental shelf during the last millennium and its relationship with atmospheric conditions

NASA Astrophysics Data System (ADS)

Briceño, F. J., Sr.; Sifeddine, A.

2015-12-01

We present a record of laminated sediment cores retrieved in the Pisco region (14 °S) characterized by local aeolian inputs. This record covers the Medieval Climate Anomaly (MCA) to Little Ice Age (LIA) and the Current Warm Period (CWP) at centennial to sub-decadal resolution. The aim of the study is to reconstruct the patterns of aeolian sedimentation as well as the most important processes that control the input of this material to understand how these components reflect atmospheric climate variability during the last millennium. Assuming that the mineral fraction of the sediment is composed of several lognormally distributed particle populations, we applied an iterative least-square fitting routine to determine the number and the characteristics of the individual particles populations. This allows inferring the spatial and temporal variation of particles populations and thus transport mechanisms involved. Two components with grain size modes at 54±11 μm and 90±11 μm related with local aeolian erosion over the Pisco region were found. Our results showed active aeolian erosion during the second half of the MCA and rapid decrease from the MCA to the LIA. During the LIA the aeolian deposition exhibited a decreasing activity. During the CWP the aeolian deposition increased progressively. Comparison with others South American records indicates that those changes are linked to change in the meridional position of the Intertropical convergence zone (ITCZ) and South Pacific Subtropical High (SPSH) at the centennial time resolution. Finally the CWP period showed an increase in the aeolian deposition and thus in the wind intensity over the past two centuries. This likely represents the result of the modern position of the ITCZ-SPSH system and the associated intensification of the local and regional winds. Nevertheless, the aeolian deposition and in consequence the wind intensity and variability of the last 100 yr are stronger than during the second sequence of the MCA

Laboratory and field performance of a laser particle counter for measuring aeolian sand transport

NASA Astrophysics Data System (ADS)

Hugenholtz, Chris H.; Barchyn, Thomas E.

2011-03-01

This paper reports the results of laboratory and field tests that evaluate the performance of a new laser particle counter for measuring aeolian sand transport. The Wenglor® model YH03PCT8 ("Wenglor") consists of a laser (655 nm), photo sensor, and switching circuit. When a particle passes through the 0.6 mm diameter, 30 mm long laser beam, the sensor outputs a digital signal. Laboratory tests with medium sand and a vertical gravity flume show that the Wenglor count rate scales approximately linearly with mass flux up to the saturation point of the sensor, after which the count rate decreases despite increasing mass flux. Saturation depends on the diameter and concentration of particles in the airstream and may occur during extreme events in the field. Below saturation sensor performance is relatively consistent; the mean difference between average count rate response was between 50 and 100 counts. Field tests provide a complimentary frame of reference for evaluating the performance of the Wenglor under varying environmental conditions and to gauge its performance with respect to a collocated piezoelectric impact sensor (Sensit H11-B). During 136.5 h of deployment on an active sand dune the relative proportion of time sand transport recorded by two Wenglors was 0.09% and 0.79%, compared to 4.68% by the Sensit H11-B. The weak performance of the Wenglors is attributed to persistent lens contamination from adhesion of sand grains on the sensors after rainfall. However, during dry and windy conditions the Wenglor performance improved substantially; sensors measured a concentration of sand particles in the airstream more than seven times greater than that measured by the Sensit. Between the two Wenglors, the mean absolute count rate difference was 6.16 counts per second, with a standard deviation of 8.53 counts per second. For short-term measurement campaigns in dry conditions, therefore, the Wenglor is relatively consistent and can outperform the Sensit in detecting

Aeolian process of the dried-up riverbeds of the Hexi Corridor, China: a wind tunnel experiment.

PubMed

Zhang, Caixia; Wang, Xunming; Dong, Zhibao; Hua, Ting

2017-08-01

Wind tunnel studies, which remain limited, are an important tool to understand the aeolian processes of dried-up riverbeds. The particle size, chemical composition, and the mineral contents of sediments arising from the dried river beds are poorly understood. Dried-up riverbeds cover a wide area in the Hexi Corridor, China, and comprise a complex synthesis of different land surfaces, including aeolian deposits, pavement surfaces, and Takyr crust. The results of the present wind tunnel experiment suggest that aeolian transport from the dried-up riverbeds of the Hexi Corridor ranges from 0 to 177.04 g/m 2 /min and that dry riverbeds could be one of the main sources of dust emissions in this region. As soon as the wind velocity reaches 16 m/s and assuming that there are abundant source materials available, aeolian transport intensity increases rapidly. The dried-up riverbed sediment and the associated aeolian transported material were composed mainly of fine and medium sands. However, the transported samples were coarser than the bed samples, because of the sorting effect of the aeolian processes on the sediment. The aeolian processes also led to regional elemental migration and mineral composition variations.

Gravel and sand resources of the New England-New York region

USGS Publications Warehouse

Currier, Louis W.

1955-01-01

Deposits of sand and gravel are widespread in the New England-New York regions and constitute one of its principal mineral resources. Most of the pits are operated intermittently to supply local needs. Because of the great number and variety of known deposits, and because they have been worked at countless points it is impracticable to describe in detail either the deposits or the individual pits. On the other hand, a broad description of the geologic modes of occurrence with relation to the regional geology will serve adequately to indicate the importance of the resource in the regional economy and development. Except for some special sands, such as "glass sand", certain molding and foundry sands, et. al., for which restrictive textural, compositional and physical properties are required, sand and gravel are used chiefly for local construction and are not commonly transported for long distances. Sand and gravel deposits of the region fall into four principal genetic categories - e.g., glacial, alluvial, marine, and aeolian. Of these, deposits of glacial origin are by far the most widespread and important.

Gully annealing by aeolian sediment: field and remote-sensing investigation of aeolian-hillslope-fluvial interactions, Colorado River corridor, Arizona, USA

USGS Publications Warehouse

Sankey, Joel B.; Draut, Amy E.

2014-01-01

Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This study of gully annealing by aeolian sediment, spanning 95 km along the Colorado River corridor in Glen, Marble, and Grand Canyon, Arizona, USA, employed field and remote sensing observations, including digital topographic modelling. Results indicate that aeolian sediment activity can be locally effective at counteracting gully erosion. Gullies are less prevalent in areas where surficial sediment undergoes active aeolian transport, and have a greater tendency to terminate in active aeolian sand. Although not common, examples exist in the record of historical imagery of gullies that underwent infilling by aeolian sediment in past decades and evidently were effectively annealed. We thus provide new evidence for a potentially important interaction of aeolian–hillslope–fluvial processes, which could affect dryland regions substantially in ways not widely recognized. Moreover, because the biologic soil crust plays an important role in determining aeolian sand activity, and so in turn the extent of gully development, this study highlights a critical role of geomorphic–ecologic interactions in determining arid-landscape evolution.

A new record of late Pliocene-early Pleistocene aeolian loess-red clay deposits from the western Chinese Loess Plateau and its palaeoenvironmental implications

NASA Astrophysics Data System (ADS)

Zan, Jinbo; Fang, Xiaomin; Zhang, Weilin; Yan, Maodu; Zhang, Dawen

2018-04-01

The loess-red clay sequences in northern China provide high-resolution terrestrial records of Asian monsoon evolution and aridification of the Asian interior. To date, however, aeolian deposits of late Pliocene-early Pleistocene age (3.5-2.4 Ma) have only rarely been reported from the western Chinese Loess Plateau (CLP), which significantly hinders our understanding of the distribution of aeolian deposits and the palaeoenvironmental evolution of the region. Here, we present magnetostratigraphic, lithologic and magnetic susceptibility results for two recently-drilled boreholes from the north bank of Baxie River, central Linxia Basin, which are highly correlative with those of the loess-red clay deposits spanning the interval from 3.6 to 2.4 Ma in the eastern CLP. Our results provide the first direct evidence for the occurrence of late Pliocene-early Pleistocene aeolian deposits in the western CLP and provide new insights into the distribution of aeolian deposits in northern China. The spatial coherence of the magnetic susceptibility fluctuations further indicates that magnetic susceptibility is a powerful tool for stratigraphic correlation of late Pliocene aeolian deposits in the western CLP. In addition, our results demonstrate that erosional events may have occurred in the early or middle Pleistocene, and they may provide new insights into the reasons for the absence of loess-red clay deposits from 3.5 to 2.4 Ma in most parts of the western CLP.

A Late Pleistocene linear dune dam record of aeolian-fluvial dynamics at the fringes of the northwestern Negev dunefield

NASA Astrophysics Data System (ADS)

Roskin, Joel; Bookman, Revital; Friesem, David; Vardi, Jacob

2017-04-01

The paper presents a late Pleistocene aeolian-fluvial record within a linear dune-like structure that partway served as a dune dam. Situated along the southern fringe of the northwestern Negev desert dunefield (Israel) the structure's morphology, orientation, and some of its stratigraphic units partly resemble adjacent west-east extending vegetated linear dunes. Uneven levels of light-colored, fine-grained fluvial deposits (LFFDs) extend to the north and south from the flanks of the studied structure. Abundant Epipalaeolithic sites line the fringes of the LFFDs. The LFFD microstructures of fine graded bedding and clay blocky peds indicate sorting and shrinking of saturated clays in transitional environments between low energy flows to shallow standing water formed by dunes damming a mid-sized drainage system. The structure's architecture of interchanging units of sand with LFFDs indicates interchanging dominances between aeolian sand incursion and winter floods. Sand mobilization associated with powerful winds during the Heinrich 1 event led to dune damming downstream of the structure and within the structure to in-situ sand deposition, partial fluvial erosion, reworking of the sand, and LFFD deposition. Increased sand deposition led to structure growth and blockage of its drainage system that in turn accumulated LFFD units up stream of the structure. Extrapolation of current local fluvial sediment yields indicate that LFFD accretion up to the structure's brim occurred over a short period of several decades. Thin layers of Geometric Kebaran (c. 17.5-14.5 ka cal BP) to Harifian (12-11 ka BP) artifacts within the structure's surface indicates intermittent, repetitive, and short term camping utilizing adjacent water along a timespan of 4-6 kyr. The finds directly imply that the NW Negev LFFDs formed in dune-dammed water bodies which themselves were formed following events of vegetated linear dune elongation. LFFD accumulation persisted as a result of dune dam

Source-to-sink cycling of aeolian sediment in the north polar region of Mars

NASA Astrophysics Data System (ADS)

Ewing, R. C.; Kocurek, G.

2012-12-01

Aeolian sand dunes are prominent features on the landscapes of Earth, Mars, Venus and Titan and sedimentary deposits interpreted as aeolian in origin are found in the rock records of Earth and Mars. The widespread occurrence of aeolian dunes on the surface of these worlds and within their deep-time depositional records suggests that aeolian systems are and likely have been a default depositional environment for the Solar System. Within an aeolian source-to-sink context, we hypothesize that planet-specific boundary conditions strongly impact production, transport, accumulation and preservation of aeolian sediment, whereas dunes and dune-field patterns remain largely similar. This hypothesis is explored within the north polar region of Mars, which hosts the most extensive aeolian dune fields and aeolian sedimentary deposits yet recognized on Mars and appears to be a region of dynamic source-to-sink cycling of aeolian sediments. The Planum Boreum Cavi Unit rests beneath north polar ice cap of Mars and is composed of several hundred meters of niveo-aeolian dune cross-stratification. The overall architecture of the unit consists of sets of preserved dune topography with an upward increase in the abundance of ice. Dune sets are defined by stabilized, polygonally fractured bounding surfaces, erosional bounding surfaces and typical internal lee foresets made of sediment and ice. The accumulation of the Cavi Unit is interpreted as occurring through freezing and serves as an example of a cold temperature boundary condition on aeolian sediment accumulation. Preservation of the Cavi Unit arises because of deposition of the overlying ice cap and contrasts with preservation of aeolian sediment on Earth, which is largely driven by eustasy and tectonics. The Cavi Unit is thought to be one source of sediment for the north polar Olympia Undae Dune Field. The region of Olympia Undae near the Cavi Unit shows a reticulate dune field pattern composed of two sets of nearly orthogonal

Curiosity at Gale crater, Mars: characterization and analysis of the Rocknest sand shadow.

PubMed

Blake, D F; Morris, R V; Kocurek, G; Morrison, S M; Downs, R T; Bish, D; Ming, D W; Edgett, K S; Rubin, D; Goetz, W; Madsen, M B; Sullivan, R; Gellert, R; Campbell, I; Treiman, A H; McLennan, S M; Yen, A S; Grotzinger, J; Vaniman, D T; Chipera, S J; Achilles, C N; Rampe, E B; Sumner, D; Meslin, P-Y; Maurice, S; Forni, O; Gasnault, O; Fisk, M; Schmidt, M; Mahaffy, P; Leshin, L A; Glavin, D; Steele, A; Freissinet, C; Navarro-González, R; Yingst, R A; Kah, L C; Bridges, N; Lewis, K W; Bristow, T F; Farmer, J D; Crisp, J A; Stolper, E M; Des Marais, D J; Sarrazin, P

2013-09-27

The Rocknest aeolian deposit is similar to aeolian features analyzed by the Mars Exploration Rovers (MERs) Spirit and Opportunity. The fraction of sand <150 micrometers in size contains ~55% crystalline material consistent with a basaltic heritage and ~45% x-ray amorphous material. The amorphous component of Rocknest is iron-rich and silicon-poor and is the host of the volatiles (water, oxygen, sulfur dioxide, carbon dioxide, and chlorine) detected by the Sample Analysis at Mars instrument and of the fine-grained nanophase oxide component first described from basaltic soils analyzed by MERs. The similarity between soils and aeolian materials analyzed at Gusev Crater, Meridiani Planum, and Gale Crater implies locally sourced, globally similar basaltic materials or globally and regionally sourced basaltic components deposited locally at all three locations.

Aeolian drift sand archives show evidence of Late Holocene groundwater dynamics in NE Belgium

NASA Astrophysics Data System (ADS)

Beerten, Koen

2017-04-01

The sandy unconfined aquifers of NE Belgium (Kleine Nete catchment, Campine area) underlay a flat and slightly undulating landscape. It is drained by small rivers that occupy shallow valleys separated by weakly expressed interfluves. Instrumental time series (collected since the 1980s) show that the mean highest groundwater table (MHG) on these interfluves (late winter - early spring) is generally 1-2 m below the surface. For earlier periods there are no systematic observations of groundwater tables in the area. Such information would allow to extend the time window for hydrological model validation and verification under different boundary conditions (soil, land-use, climate) and thus build confidence in future hydrological predictions. The sandy interfluves of the Kleine Nete catchment have witnessed strong aeolian morphodynamics during the last few millenia. Many of the podzols that developed during the Holocene became either eroded by wind deflation or buried under drift sand. This situation provides a unique means to study palaeohydrological features, events and processes in such shallow unsaturated zones. Therefore, the aim of this presentation is to explore the potential of pedological, geomorphological and historical archives from drift sand landscapes in the Campine area as proxies for past groundwater tables. The adopted approach includes a wide variety of techniques, such as field descriptions of palaeosol profile morphology, optically stimulated luminescence (OSL) dating of intercalated drift sands, determination of groundwater-controlled blow-out surfaces and observations of surface water bodies on historical maps. The buried podzols often display hydromorphic properties, such as redoximorphic features, vague horizon boundaries and peat development. OSL dating of associated drift sands suggests that a very shallow MHG existed from ca. 6 ka until at least ca. 2 ka. Subsequently, historical maps suggest that groundwater tables started to decline during

Temporal and spatial variability of aeolian sand transport: Implications for field measurements

NASA Astrophysics Data System (ADS)

Ellis, Jean T.; Sherman, Douglas J.; Farrell, Eugene J.; Li, Bailiang

2012-01-01

Horizontal variability is often cited as one source of disparity between observed and predicted rates of aeolian mass flux, but few studies have quantified the magnitude of this variability. Two field projects were conducted to evaluate meter-scale spatial and temporal in the saltation field. In Shoalhaven Heads, NSW, Australia a horizontal array of passive-style sand traps were deployed on a beach for 600 or 1200 s across a horizontal span of 0.80 m. In Jericoacoara, Brazil, traps spanning 4 m were deployed for 180 and 240 s. Five saltation sensors (miniphones) spaced 1 m apart were also deployed at Jericoacoara. Spatial variation in aeolian transport rates over small spatial and short temporal scales was substantial. The measured transport rates ( Q) obtained from the passive traps ranged from 0.70 to 32.63 g/m/s. When considering all traps, the coefficient of variation ( CoV) values ranged from 16.6% to 67.8%, and minimum and maximum range of variation coefficient ( RVC) values were 106.1% to 152.5% and 75.1% to 90.8%, respectively. The miniphone Q and CoV averaged 47.1% and 4.1% for the 1260 s data series, which was subsequently sub-sampled at 60-630 s intervals to simulate shorter deployment times. A statistically significant ( p < 0.002), inverselinear relationship was found between sample duration and CoV and between Q and CoV, the latter relationship also considering data from previous studies.

Aeolian processes in Proctor Crater on Mars: Sedimentary history as analyzed from multiple data sets

USGS Publications Warehouse

Fenton, L.K.; Bandfield, J.L.; Ward, A.W.

2003-01-01

Proctor Crater is a 150 km diameter crater in Noachis Terra, within the southern highlands of Mars. The analysis leading to the sedimentary history incorporates several data sets including imagery, elevation, composition, and thermal inertia, mostly from the Mars Global Surveyor mission. The resulting stratigraphy reveals that the sedimentary history of Proctor Crater has involved a complex interaction of accumulating and eroding sedimentation. Aeolian features spanning much of the history of the crater interior dominate its surface, including large erosional pits, stratified beds of aeolian sediment, sand dunes, erosional and depositional streaks, dust devil tracks, and small bright bed forms that are probably granule ripples. Long ago, up to 450 m of layered sediment filled the crater basin, now exposed in eroded pits on the crater floor. These sediments are probably part of an ancient deposit of aeolian volcaniclastic material. Since then, some quantity of this material has been eroded from the top layers of the strata. Small, bright dune forms lie stratigraphically beneath the large dark dune field. Relative to the large dark dunes, the bright bed forms are immobile, although in places, their orientations are clearly influenced by the presence of the larger dunes. Their prevalence in the crater and their lack of compositional and thermal distinctiveness relative to the crater floor suggests that these features were produced locally from the eroding basin fill. Dust devil tracks form during the spring and summer, following a west-southwesterly wind. Early in the spring the dust devils are largely restricted to dark patches of sand. As the summer approaches, dust devil tracks become more plentiful and spread to the rest of the crater floor, indicating that the entire region acquires an annual deposit of dust that is revealed by seasonal dust devils. The dark dunes contain few dust devil tracks, suggesting that accumulated dust is swept away directly by saltation

Curiosity at Gale Crater, Mars: Characterization and Analysis of the Rocknest Sand Shadow

NASA Technical Reports Server (NTRS)

Blake, David F.; Morris, Richard V.; Kocurek, G.; Morrison, S. M.; Downs, R. T.; Bish, D.; Ming, D. W.; Edgett, K. S.; Rubin, D.; Goetz, W.;

Field testing, comparison, and discussion of five aeolian sand transport measuring devices operating on different measuring principles

NASA Astrophysics Data System (ADS)

Goossens, Dirk; Nolet, Corjan; Etyemezian, Vicken; Duarte-Campos, Leonardo; Bakker, Gerben; Riksen, Michel

2018-06-01

Five types of sediment samplers designed to measure aeolian sand transport were tested during a wind erosion event on the Sand Motor, an area on the west coast of the Netherlands prone to severe wind erosion. Each of the samplers operates on a different principle. The MWAC (Modified Wilson And Cooke) is a passive segmented trap. The modified Leatherman sampler is a passive vertically integrating trap. The Saltiphone is an acoustic sampler that registers grain impacts on a microphone. The Wenglor sampler is an optical sensor that detects particles as they pass through a laser beam. The SANTRI (Standalone AeoliaN Transport Real-time Instrument) detects particles travelling through an infrared beam, but in different channels each associated with a particular grain size spectrum. A procedure is presented to transform the data output, which is different for each sampler, to a common standard so that the samplers can be objectively compared and their relative efficiency calculated. Results show that the efficiency of the samplers is comparable despite the differences in operating principle and the instrumental and environmental uncertainties associated to working with particle samplers in field conditions. The ability of the samplers to register the temporal evolution of a wind erosion event is investigated. The strengths and weaknesses of the samplers are discussed. Some problems inherent to optical sensors are looked at in more detail. Finally, suggestions are made for further improvement of the samplers.

Exploring how sand ramps respond to Quaternary environmental change in Southern Africa

NASA Astrophysics Data System (ADS)

Rowell, Alex; Thomas, David; Bailey, Richard

2014-05-01

The current climate of southern Africa is particularly complex and interesting due to the interaction of several climatic systems. However, reconstructions of how these systems behaved in the past, and how the environment responded, have been hampered by a general paucity of records and poor chronological control. Sand ramps may provide the potential to improve palaeoenvironmental reconstructions of southern Africa (and beyond). Formed against a topographic barrier, sand ramps include a combination of aeolian, fluvial and colluvial deposits in varying proportions. Therefore, they have the potential to record changes in moisture availability, circulation patterns and sediment supply which can be independently dated using luminescence dating. Nevertheless relatively little attention has been paid to these features and thus the environmental controls on their formation are not yet fully understood. In particular, there is debate as to whether they reflect deposition during a 'window of opportunity' in which high-magnitude, low-frequency events are recorded (Bateman et al. 2012) or whether they record more gradual, cyclic climate change (Bertram, 2003) or even if there is a uniform control on their formation. This research aims to investigate how sand ramps respond to environmental change and what they can tell us about the paleoenvironment of southern Africa. This poster displays preliminary results based on initial field investigation. This confirmed sand ramps to be ubiquitous in southern Africa and that they record a complex interaction of aeolian, fluvial and colluvial deposits which appears to differ between sand ramps. Preliminary luminescence dating results and sedimentology are displayed for two sand ramps, one from south west Namibia the other from the Karoo region of South Africa.

Geochemical evidence for the provenance of aeolian deposits in the Qaidam Basin, Tibetan Plateau

NASA Astrophysics Data System (ADS)

Du, Shisong; Wu, Yongqiu; Tan, Lihua

2018-06-01

The main purpose of this study is to analyse the material source of different grain-size components of dune sand in the Qaidam Basin. We determined the trace and rare earth element (REE) compositions and Sr-Nd isotopic compositions of the coarse (75-500 μm) and fine (<75 μm) fractions of surface sediment samples. The comparison of the immobile trace element and REE compositions, Sr-Nd isotopic compositions and multidimensional scaling (MDS) results of the dune sands with those of different types of sediments in potential source areas revealed the following information. (1) The fine- and coarse-grained fractions of dune sands in the Qaidam Basin exhibit distinctly different elemental concentrations, elemental patterns and characteristic parameters of REE. Moreover, Sr-Nd isotopic differences also exist between different grain-size fractions of aeolian sand, which means that different grain-size fractions of these dune sands have different source areas. (2) The geochemical characteristics of the coarse particles of dune sand exhibit obvious regional heterogeneity and generally record a local origin derived from local fluvial sediments and alluvial/proluvial sediments. The coarse- and fine-grained dune sand in the southern Qaidam Basin mainly came from Kunlun Mountains, whereas the coarse- and fine-grained dune sand in the northeastern Qaidam Basin mainly came from Qilian Mountains. (3) The fine-grained fractions of sediments throughout the entire Qaidam Basin may have been affected by the input of foreign materials from the Tarim Basin.

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

flat seaming the toes of the fan chain. Sedimentation is characterized by flashy discharge with many episodic flood pulses of short periodicity and mainly rapid waning of high-water phases with quick underrunning of the threshold velocity for keeping the large clasts rolling. Pronounced slack water episodes allow occasionally the draping of gravel sheets with thin veneers of waning-flow and stagnant-water fines. Spectacular invertebrate burrows in finer breccias underline the flashy nature of most of the flood and flow events, allowing the colonization of the sediments with ground-living invertebrates during interruptions of transport and accumulation. Some peculiar dewatering structures being infilling of crack systems in breccias with wash-load sand are probably induced by earthquake shocks thus pointing to the active tectonic setting of the depositional area. Aeolian sands originate as transverse dune ridges in restricted dune fields and extensive sand seas and as sheet sands in interdune playa depressions. Associated mudstones and ventifact gravel form in wet interdunes or in playa lakes and in deflationary interdunes, respectively. Accumulation of aeolian dunes and interdune sheet sands takes place by both spreading out of drapes on flats and infilling of abandoned fluvial channels which enhance the trapping of sand by topographical effects. The dunes and wind ripple trains migrate across dry interdune floors under predominantly unidirectional winds. Sedimentary processes are grainfall and grainflow on the lee slope of dunes and subcritical climbing of wind ripples. Episodical wetting and dampening of dry interdune flats by intermittent rainfall, periodical dew and even ephemeral fluvial or alluvial-fan incursions allow formation of adhesion-rippled sands on damp surfaces and origin of sandy and silty-clayey lacustrine sediments in shallow water veneers of the flooded playa. Aquatic modification of aeolian sands by invading flood surges of atmospheric or alluvial

Vegetation and substrate properties of aeolian dune fields in the Colorado River corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Draut, Amy E.

2011-01-01

This report summarizes vegetation and substrate properties of aeolian landscapes in the Colorado River corridor through Grand Canyon, Arizona, in Grand Canyon National Park. Characterizing these parameters provides a basis from which to assess future changes in this ecosystem, including the spread of nonnative plant species. Differences are apparent between aeolian dune fields that are downwind of where modern controlled flooding deposits new sandbars (modern-fluvial-sourced dune fields) and those that have received little or no new windblown sand since river regulation began in the 1960s (relict-fluvial-sourced dune fields). The most substantial difference between modern- and relict-fluvial-sourced aeolian dune fields is the greater abundance of biologic soil crust in relict dune fields. These findings can be used with similar investigations in other geomorphic settings in Grand Canyon and elsewhere in the Colorado River corridor to evaluate the health of the Colorado River ecosystem over time.

Downslope coarsening in aeolian grainflows of the Navajo Sandstone

NASA Astrophysics Data System (ADS)

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

2012-07-01

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

Aeolian transport in the field: A comparison of the effects of different surface treatments

NASA Astrophysics Data System (ADS)

Dong, Zhibao; Lv, Ping; Zhang, Zhengcai; Qian, Guangqiang; Luo, Wanyin

2012-05-01

Aeolian transport represents the result of wind-surface interactions, and therefore depends strongly on variations in the characteristics of the sediment surface. We conducted field observations of aeolian transport of typical dune sand in three 80 m × 80 m plots with different surface treatments: gravel-covered sand, enclosed shifting sand, and open (unprotected) shifting sand. The study was performed at the Shapotou Aeolian Experiment Site in the southeastern part of China's Tengger Desert to compare the effects of these different surface treatments on aeolian transport. To do so, we analyzed the flux density profiles and transport rates above each surface. The flux density profiles for all three treatments followed the exponential decay law that was proposed by most previous researchers to describe the saltation flux density profiles. Coefficients of the exponential decay function were defined as a function of the surface and the wind velocity. The enclosed and open plots with shifting sand had similar flux density profiles, but the flux density above gravel-covered plots showed that transport decayed more slowly with increasing height, producing flux density profiles with a higher average saltation height. The transport rate above the three treatment plots tended to increase proportionally with the cube of the mean wind velocity and with the maximum wind velocity during the observation period, but was more strongly correlated with the square of drift potential. Transport rates above the plot with open shifting sand were greater than those above the plots with enclosed shifting sand and the gravel-covered plot.

River of Sand

NASA Image and Video Library

2016-09-21

A dominant driver of surface processes on Mars today is aeolian (wind) activity. In many cases, sediment from this activity is trapped in low-lying areas, such as craters. Aeolian features in the form of dunes and ripples can occur in many places on Mars depending upon regional wind regimes. The Cerberus Fossae are a series of discontinuous fissures along dusty plains in the southeastern region of Elysium Planitia. This rift zone is thought to be the result of combined volcano-tectonic processes. Dark sediment has accumulated in areas along the floor of these fissures as well as inactive ripple-like aeolian bedforms known as "transverse aeolian ridges" (TAR). Viewed through HiRISE infrared color, the basaltic sand lining the fissures' floor stands out as deep blue against the light-toned dust covering the region. This, along with the linearity of the fissures and the wave-like appearance of the TAR, give the viewer an impression of a river cutting through the Martian plains. However, this river of sand does not appear to be flowing. Analyses of annual monitoring images of this region have not detected aeolian activity in the form of ripple migration thus far. http://photojournal.jpl.nasa.gov/catalog/PIA21063

Building of tropical beach ridges, northeastern Queensland, Australia: Cyclone inundation and aeolian decoration

NASA Astrophysics Data System (ADS)

Tamura, Toru; Nicholas, William; Brooke, Brendan; Oliver, Thomas

2016-04-01

Processes associated with tropical cyclones are thought responsible for building coarse sand beach ridges along the northeastern Queensland coast, Australia. While these ridges are expected to be geological records of the past cyclone, they question the general consensus of the aeolian genesis of sandy beach ridges. To explore the ridge-forming process, we carried out the GPR survey, auger drilling, pit excavation, grain-size analysis, and OSL dating for coarse sand beach ridges at the Cowley Beach, northeastern Queensland. The Cowley Beach is a mesotidal beach characterized by a low-tide terrace and steep beach face. Ten beach ridges are recognized along the survey transect that extends 700 m inland from the shore. 37 OSL ages are younger seawards, indicating the seaward accretion of the ridge sequence over the last 2700 years. The highest ridge is +5.1 m high above AHD (Australian Height Datum). Two GPR units are bounded by a groundwater surface at c. +1.5 m AHD. The upper unit is characterized by horizontal to hummocky reflectors punctuated by seaward dipping truncation surfaces. These reflectors in places form dome-like structure that appears to be the nucleus of a beach ridge. The shape and level (+2.5 m AHD) of the dome are similar to those of the present swash berm. The lower unit shows a sequence of reflectors that dip at an angle of present beach face. The sequence is dissected by truncation surfaces, some of which are continuous to those in the upper unit. Coarse sand mainly forms beach ridge deposits below +4.0 m AHD, while a few higher ridges have an upward fining layer composed of medium sand above +4.0 m, which is finer than aeolian ripples found on the backshore during the survey. In addition, pumice gravel horizons underlie the examined ridge crests. The sequence of seaward dipping reflectors indicates that the Cowley Beach, like other many sandy beaches, has prograded during onshore sand accretion by fairweather waves and has been eroded by storms

Provenance and recycling of Arabian desert sand

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Vermeesch, Pieter; Andò, Sergio; Vezzoli, Giovanni; Valagussa, Manuel; Allen, Kate; Kadi, Khalid; Al-Juboury, Ali

2013-04-01

This study seeks to determine the ultimate origin of aeolian sand in Arabian deserts by high-resolution petrographic and heavy-mineral techniques combined with zircon U-Pb geochronology. Point-counting is used here as the sole method by which unbiased volume percentages of heavy minerals can be obtained. A comprehensive analysis of river and wadi sands from the Red Sea to the Bitlis-Zagros orogen allowed us to characterize all potential sediment sources, and thus to quantitatively constrain provenance of Arabian dune fields. Two main types of aeolian sand can be distinguished. Quartzose sands with very poor heavy-mineral suites including zircon occupy most of the region comprising the Great Nafud and Rub' al-Khali Sand Seas, and are largely recycled from thick Lower Palaeozoic quartzarenites with very minor first-cycle contributions from Precambrian basement, Mesozoic carbonate rocks, or Neogene basalts. Instead, carbonaticlastic sands with richer lithic and heavy-mineral populations characterize coastal dunes bordering the Arabian Gulf from the Jafurah Sand Sea of Saudi Arabia to the United Arab Emirates. The similarity with detritus carried by the axial Tigris-Euphrates system and by transverse rivers draining carbonate rocks of the Zagros indicates that Arabian coastal dunes largely consist of far-travelled sand, deposited on the exposed floor of the Gulf during Pleistocene lowstands and blown inland by dominant Shamal northerly winds. A dataset of detrital zircon U-Pb ages measured on twelve dune samples and two Lower Palaeozoic sandstones yielded fourteen identical age spectra. The age distributions all show a major Neoproterozoic peak corresponding to the Pan-African magmatic and tectonic events by which the Arabian Shield was assembled, with minor late Palaeoproterozoic and Neoarchean peaks. A similar U-Pb signature characterizes also Jafurah dune sands, suggesting that zircons are dominantly derived from interior Arabia, possibly deflated from the Wadi al

Provenance and recycling of Arabian desert sand

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Vermeesch, Pieter; Andò, Sergio; Vezzoli, Giovanni; Valagussa, Manuel; Allen, Kate; Kadi, Khalid A.; Al-Juboury, Ali I. A.

2013-05-01

This study seeks to determine the ultimate origin of aeolian sand in Arabian deserts by high-resolution petrographic and heavy-mineral techniques combined with zircon U-Pb geochronology. Point-counting is used here as the sole method by which unbiased volume percentages of heavy minerals can be obtained. A comprehensive analysis of river and wadi sands from the Red Sea to the Bitlis-Zagros orogen allowed us to characterize all potential sediment sources, and thus to quantitatively constrain provenance of Arabian dune fields. Two main types of aeolian sand can be distinguished. Quartzose sands with very poor heavy-mineral suites including zircon occupy most of the region comprising the Great Nafud and Rub' al-Khali Sand Seas, and are largely recycled from thick Lower Palaeozoic quartzarenites with very minor first-cycle contributions from Precambrian basement, Mesozoic carbonate rocks, or Neogene basalts. Instead, carbonaticlastic sands with richer lithic and heavy-mineral populations characterize coastal dunes bordering the Arabian Gulf from the Jafurah Sand Sea of Saudi Arabia to the United Arab Emirates. The similarity with detritus carried by the axial Tigris-Euphrates system and by transverse rivers draining carbonate rocks of the Zagros indicates that Arabian coastal dunes largely consist of far-travelled sand, deposited on the exposed floor of the Gulf during Pleistocene lowstands and blown inland by dominant Shamal northerly winds. A dataset of detrital zircon U-Pb ages measured on twelve dune samples and two Lower Palaeozoic sandstones yielded fourteen identical age spectra. The age distributions all show a major Neoproterozoic peak corresponding to the Pan-African magmatic and tectonic events by which the Arabian Shield was assembled, with minor late Palaeoproterozoic and Neoarchean peaks. A similar U-Pb signature characterizes also Jafurah dune sands, suggesting that zircons are dominantly derived from interior Arabia, possibly deflated from the Wadi al

Evaluation of simple geochemical indicators of aeolian sand provenance: Late Quaternary dune fields of North America revisited

USGS Publications Warehouse

Muhs, Daniel

2017-01-01

Dune fields of Quaternary age occupy large areas of the world's arid and semiarid regions. Despite this, there has been surprisingly little work done on understanding dune sediment provenance, in part because many techniques are time-consuming, prone to operator error, experimental, highly specialized, expensive, or require sophisticated instrumentation. Provenance of dune sand using K/Rb and K/Ba values in K-feldspar in aeolian sands of the arid and semiarid regions of North America is tested here. Results indicate that K/Rb and K/Ba can distinguish different river sands that are sediment sources for dunes and dune fields themselves have distinctive K/Rb and K/Ba compositions. Over the Basin and Range and Great Plains regions of North America, the hypothesized sediment sources of dune fields are reviewed and assessed using K/Rb and K/Ba values in dune sands and in hypothesized source sediments. In some cases, the origins of dunes assessed in this manner are consistent with previous studies and in others, dune fields are found to have a more complex origin than previously thought. Use of K/Rb and K/Ba for provenance studies is a robust method that is inexpensive, rapid, and highly reproducible. It exploits one of the most common minerals found in dune sand, K-feldspar. The method avoids the problem of using simple concentrations of key elements that may be subject to interpretative bias due to changes in mineralogical maturity of Quaternary dune fields that occur over time.

Holocene beach buildup and coastal aeolian sand incursions off the Nile littoral cell

NASA Astrophysics Data System (ADS)

Roskin, Joel; Sivan, Dorit; Shtienberg, Gilad; Porat, Naomi; Bookman, Revital

2017-04-01

Israel's coastal plain is abundant with sand originating from the Nile littoral cell. The inland windblown loose sand has formed 3-6 km wide lobe-like sand and dune fields currently comprised of foredunes, linear and northeasterly facing transverse and parabolic dunes that are currently stabilized by vegetation. This study reviews the architecture and history of the these dune fields aiming to: (a) Date the timings of beach accretion, and sand and dune incursions. (b) Discriminate between natural and human-induced forcing factors of sand mobilization and stabilization in time and space. (c) Present a model of the dunescape development. (d) Assess scenarios of sand transport in the future charcaterized by intense human impact and climate change. Luminescence ages, radiocarbon dates and relative ages from previously published geological and archaeological reports, historical texts, together with new optically stimulated luminescence (OSL) ages and stratigraphic and sedimentological data are analyzed. The deposition, mobilizations and preservation of the sand bodies, initially induced by the decline in sea level rise at 6-4 ka, were later controlled by historic land-use intensity and modern land-use/negligence practices. At 6 ka, beach sand buildup rapidly started. Where aeolianite ridges bordered the coast, pulses of sand with biogenic carbonate grains unconformably draped the ridges and rapidly consolidated into a distinct sandy calcarenite unit. Further east, sand sheets and low dunes partly pedogenized following their incursion, but did not cement. The water retention capacities of the sand sheets enabled the establishment of a sand-stabilizing vegetation cover that probably became an attractive environment for fuel and grazing. The growing Hellenistic-Roman-Byzantine ( 2.4-1.3 ka) populations probably led to increased consumption and massive destruction of sand stabilizing vegetation, enabling sand erodibility and mobilization during winter storms. The sand

Aeolian Processes and Features on Venus

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Bender, Kelly C.; Saunders, Stephen; Schubert, Gerald; Weitz, Catherine M.

1997-01-01

Aeolian features on Venus include dune fields, eroded hills (yardangs), wind streaks, (miniature dunes of 10 to 30 cm wavelength). Although and possibly microdunes (in repetitive imaging by Magellan did show changes in the appearance of the surface, these changes are attributed to radar artifacts as a consequence of look direction rather than to physical changes of the surface. Nonetheless, measurements of wind speeds near the surface of Venus and wind tunnel simulations suggest that aeolian processes could be currently active on Venus. Study of radar images of terrestrial analogs shows that radar wavelength, polarization, and viewing geometry, including look direction and incidence angle, all influence the detection of dunes, yardangs, and wind streaks. For best detection, dune crests and yardangs should be oriented perpendicular to look direction. Longer wavelength systems can penetrate sand sheets a meter or more thick, rendering them invisible, especially in arid regions. For wind streaks to be visible, there must be a contrast in surface properties between the streak and the background on which it occurs. Nonetheless, more than 6000 aeolian features have been found on Magellan images of Venus, the most common of which are various wind streaks. Mapping wind streak orientations enables near-surface wind patterns to be inferred for the time of their formation. Type P streaks are associated with parabolic ejecta crater deposits and are considered to have formed in association with the impact event. Most Type P streaks are oriented westward, indicative of the upper altitude superrotation winds of Venus. Non Type P streaks have occurrences and orientations consistent with Hadley circulation. Some streaks in the southern hemisphere are oriented to the northeast, suggesting a Coriolis effect.

Linking fluvial and aeolian morphodynamics in the Grand Canyon, USA

USGS Publications Warehouse

Kasprak, Alan; Bangen, Sara G.; Buscombe, Daniel; Caster, Joshua; East, Amy; Grams, Paul E.; Sankey, Joel B.

2017-01-01

In river valleys, fluvial and upland landscapes are intrinsically linked through sediment exchange between the active channel, near-channel fluvial deposits, and higher elevation upland deposits. During floods, sediment is transferred from channels to low-elevation nearchannel deposits [Schmidt and Rubin, 1995]. Particularly in dryland river valleys, subsequent aeolian reworking of these flood deposits redistributes sediment to higher elevation upland sites, thus maintaining naturallyoccurring aeolian landscapes [Draut, 2012].

Ancient Martian aeolian processes and palaeomorphology reconstructed from the Stimson formation on the lower slope of Aeolis Mons, Gale crater, Mars

USGS Publications Warehouse

Banham, Steve G.; Gupta, Sanjeev; Rubin, David M.; Watkins, Jessica A.; Sumner, Dawn Y.; Edgett, Kenneth S.; Grotzinger, John P.; Lewis, Kevin W.; Edgar, Lauren; Stack, Kathryn M.; Barnes, Robert; Bell, Jame F. III; Day, Mackenzie D.; Ewing, Ryan C.; Lapotre, Mathieu G.A.; Stein, Nathan T.; Rivera-Hernandez, Frances; Vasavada, Ashwin R.

2018-01-01

Reconstruction of the palaeoenvironmental context of Martian sedimentary rocks is central to studies of ancient Martian habitability and regional palaeoclimate history. This paper reports the analysis of a distinct aeolian deposit preserved in Gale crater, Mars, and evaluates its palaeomorphology, the processes responsible for its deposition, and its implications for Gale crater geological history and regional palaeoclimate. Whilst exploring the sedimentary succession cropping out on the northern flank of Aeolis Mons, Gale crater, the Mars Science Laboratory rover Curiosity encountered a decametre‐thick sandstone succession, named the Stimson formation, unconformably overlying lacustrine deposits of the Murray formation. The sandstone contains sand grains characterized by high roundness and sphericity, and cross‐bedding on the order of 1 m in thickness, separated by sub‐horizontal bounding surfaces traceable for tens of metres across outcrops. The cross‐beds are composed of uniform thickness cross‐laminations interpreted as wind‐ripple strata. Cross‐sets are separated by sub‐horizontal bounding surfaces traceable for tens of metres across outcrops that are interpreted as dune migration surfaces. Grain characteristics and presence of wind‐ripple strata indicate deposition of the Stimson formation by aeolian processes. The absence of features characteristic of damp or wet aeolian sediment accumulation indicate deposition in a dry aeolian system. Reconstruction of the palaeogeomorphology suggests that the Stimson dune field was composed largely of simple sinuous crescentic dunes with a height of ca10 m, and wavelengths of ca 150 m, with local development of complex dunes. Analysis of cross‐strata dip‐azimuths indicates that the general dune migration direction and hence net sediment transport was towards the north‐east. The juxtaposition of a dry aeolian system unconformably above the lacustrine Murray formation represents starkly

Granulometric profiling of aeolian dust deposits by automated image analysis

NASA Astrophysics Data System (ADS)

Varga, György; Újvári, Gábor; Kovács, János; Jakab, Gergely; Kiss, Klaudia; Szalai, Zoltán

2016-04-01

Determination of granulometric parameters is of growing interest in the Earth sciences. Particle size data of sedimentary deposits provide insights into the physicochemical environment of transport, accumulation and post-depositional alterations of sedimentary particles, and are important proxies applied in paleoclimatic reconstructions. It is especially true for aeolian dust deposits with a fairly narrow grain size range as a consequence of the extremely selective nature of wind sediment transport. Therefore, various aspects of aeolian sedimentation (wind strength, distance to source(s), possible secondary source regions and modes of sedimentation and transport) can be reconstructed only from precise grain size data. As terrestrial wind-blown deposits are among the most important archives of past environmental changes, proper explanation of the proxy data is a mandatory issue. Automated imaging provides a unique technique to gather direct information on granulometric characteristics of sedimentary particles. Granulometric data obtained from automatic image analysis of Malvern Morphologi G3-ID is a rarely applied new technique for particle size and shape analyses in sedimentary geology. Size and shape data of several hundred thousand (or even million) individual particles were automatically recorded in this study from 15 loess and paleosoil samples from the captured high-resolution images. Several size (e.g. circle-equivalent diameter, major axis, length, width, area) and shape parameters (e.g. elongation, circularity, convexity) were calculated by the instrument software. At the same time, the mean light intensity after transmission through each particle is automatically collected by the system as a proxy of optical properties of the material. Intensity values are dependent on chemical composition and/or thickness of the particles. The results of the automated imaging were compared to particle size data determined by three different laser diffraction instruments

2010 weather and aeolian sand-transport data from the Colorado River corridor, Grand Canyon, Arizona

USGS Publications Warehouse

Dealy, Timothy P.; East, Amy E.; Fairley, Helen C.

2014-01-01

Measurements of weather parameters and aeolian sand transport were made in 2010 near selected archeological sites in the Colorado River corridor through Grand Canyon, Arizona. Data collected in 2010 indicate event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Differences in weather patterns between 2009 and 2010 included a slightly later spring windy season, greater spring precipitation and annual rainfall totals, and a later onset and length of the reduced diurnal barometric-pressure fluctuations commonly associated with summer monsoon conditions. The increase in spring precipitation was consistent with the 2010 spring El Niño conditions compared to the 2009 spring La Niña conditions, whereas the subsequent transition to an El Niño-Southern Oscillation neutral phase appeared to delay the reduction in diurnal barometric fluctuations.

[Nutrient contents and microbial populations of aeolian sandy soil in Sanjiangyuan region of Qinghai Province].

PubMed

Lin, Chao-feng; Chen, Zhan-quan; Xue, Quan-hong; Lai, Hang-xian; Chen, Lai-sheng; Zhang, Deng-shan

2007-01-01

Sanjiangyuan region (the headstream of three rivers) in Qinghai Province of China is the highest and largest inland alpine wetland in the world. The study on the nutrient contents and microbial populations of aeolian sandy soils in this region showed that soil organic matter content increased with the evolution of aeolian sand dunes from un-stabilized to stabilized state, being 5.9 and 3.8 times higher in stabilized sand dune than in mobile and semi-stabilized sand dunes, respectively. Soil nitrogen and phosphorus contents increased in line with the amount of organic matter, while potassium content and pH value varied slightly. The microbial populations changed markedly with the development of vegetation, fixing of mobile sand, and increase of soil nutrients. The quantities of soil bacteria, fungi and actinomycetes were 4.0 and 2.8 times, 19.6 and 6.3 times, and 12.4 and 2.6 times higher in stabilized and semi-stabilized sand dunes than in mobile sand dune, respectively, indicating that soil microbial bio-diversity was increased with the evolution of aeolian sand dunes from mobile to stabilized state. In addition, the quantities of soil microbes were closely correlated with the contents of soil organic matter, total nitrogen, and available nitrogen and phosphorus, but not correlated with soil total phosphorus, total and available potassium, or pH value.

Erosion and Deposition in Schaeberle Crater

NASA Image and Video Library

2016-01-14

Schaeberle Crater is a large, heavily-infilled crater with many interesting features. This image NASA Mars Reconnaissance Orbiter spacecraft shows a window into the crater fill deposit, showcasing eroding bedrock and aeolian landforms. This pit is located near the geometric center of our image, making it a central pit crater. Central pit craters are thought to form from impact melt draining through subsurface cracks in the deepest part of the crater shortly following impact. A closeup image shows light-toned bedrock and a small cliff that appears to be weathering away. Below the cliff there are several different types of aeolian features, including ripples and transverse aeolian ridges (TAR). The sand that forms the small, bluish ripples may be weathering out of the cliff face, in contrast to the larger, light-toned TAR which are thought to be currently inactive. More of the TAR are visible in another closeup image. In this case, they are clearly covered by a dark, ripple-covered sand sheet. We have only imaged this location once, so it is impossible to determine whether or not the sand sheet is blowing in the wind. But due to repeated HiRISE imaging in other areas, active dunes are now known to be common across Mars and we can reasonably speculate that these dunes are moving, too. http://photojournal.jpl.nasa.gov/catalog/PIA20339

Depositional settings of sand beaches along whitewater rivers

USGS Publications Warehouse

Vincent, K.R.; Andrews, E.D.

2008-01-01

The numbers and sizes of sand beaches suitable for recreation along selected whitewater rivers in the western United States depend on sand concentrations, range of discharge and the size, frequency and type of depositional settings. River-width expansions downstream from constrictions are the predominant depositional setting for sand beaches in the upper Grand Canyon and along five Wild and Scenic Rivers in Idaho, but not along other rivers. Beaches located upstream from constrictions are rare, in general, except in the Grand Canyon. Beaches found in expansions without constrictions dominate depositional sites along the Yampa and Green Rivers, are fairly common along the rivers in Idaho, but are relatively rare in the Grand Canyon. The magnitude of flow expansion is a reliable predictor of beach size. Beaches located on the inside of curves are uncommon, in general, but can be important recreation sites. The mid-channel bar setting is the least important from a recreation standpoint because that setting is rare and beaches there are typically small, and emergent only at low flow. The frequency of beaches is highly variable among rivers and the concentration of sand in transport is only partially responsible. Of the rivers studied, the unregulated Yampa River carries the highest concentrations of suspended sand and has among the most beaches (1.2 beaches km-1). Emergent sand beaches are essentially nonexistent along the Deschutes River and are rare along other Oregon rivers, yet these rivers transport some sand. Sand beaches are fairly common (0.8-1.1 beaches km-1) along the regulated Colorado River, but are comparatively rare (0.6 beaches km-1) along the unregulated Middle Fork Salmon River. The suspended sand concentrations in study reaches of these two rivers are similar, and the difference in the frequency of beaches may be largely because the processes that create beach-deposition settings are less active along the Middle Fork Salmon.

Robotic Measurement of Aeolian Processes

NASA Astrophysics Data System (ADS)

Roberts, S.; Duperret, J. M.; Jerolmack, D. J.; Lancaster, N.; Nikolich, G.; Shipley, T. F.; Van Pelt, R. S.; Zobeck, T. M.; Koditschek, D. E.

2015-12-01

Local and regional measurements of sand transport and dust emission in complex natural settings presently lack spatiotemporal resolution adequate to inform models relevant for land management, climate policy, and the basic science of geomorphology. Deployments of wind, sand and dust sensors sophisticated enough to begin unpacking the complex relations among wind turbulence, surface roughness, sand flux and dust emission remain largely stationary. Aerial observations from satellites, planes and even UAVs help fill in, but none of these modalities offer the hope of "capturing the action" by being at the right place at the right time relative to the highly localized nature of sediment transport during wind storms. We have been developing a legged robot capable of rapidly traversing desert terrain, and are now adapting it to serve as a platform for scientific instrumentation. We aim to field a semi-autonomous, reactive mobile sensory package suited to the needs of aeolian science that can address the limitations of existing alternatives. This presentation reports on early trials in the Jornada LTER and White Sands National Monument aimed at gathering measurements of airflow and rates of sand transport on a dune face, assessing the role of roughness elements such as vegetation in modifying the wind shear stresses incident on the surface, and estimating erosion susceptibility in a natural arid soil. We will solicit ideas from the audience about other potentially interesting and viable measurement targets. Future close collaboration between aeolian, cognitive and robotics scientists such as we hope to promote through this presentation may yield machines with scientifically relevant sensory suites possessing sufficient autonomy to operate in-situ at the most intense episodes of wind and sediment movement under conditions far too uncomfortable and hazardous for human presence.

Aeolian features and processes at the Mars Pathfinder landing site

USGS Publications Warehouse

Greeley, Ronald; Kraft, Michael; Sullivan, Robert; Wilson, Gregory; Bridges, Nathan; Herkenhoff, Ken; Kuzmin, Ruslan O.; Malin, Michael; Ward, Wes

1999-01-01

The Mars Pathfinder landing site contains abundant features attributed to aeolian, or wind, processes. These include wind tails, drift deposits, duneforms of various types, ripplelike features, and ventifacts (the first clearly seen on Mars). Many of these features are consistant with formation involving sand-size particles. Although some features, such as dunes, could develop from saltating sand-size aggregates of finer grains, the discovery of ventifact flutes cut in rocks strongly suggests that at least some of the grains are crystalline, rather than aggregates. Excluding the ventifacts, the orientations of the wind-related features correlate well with the orientations of bright wind steaks seen on Viking Orbiter images in the general area. They also correlate with wind direction predictions from the NASA-Ames General Circulation Model (GCM) which show that the strongest winds in the area occur in the northern hemisphere winter and are directed toward 209°. Copyright 1999 by the American Geophysical Union.

The geomorphology and evolution of aeolian landforms within a river valley in a semi-humid environment: A case study from Mainling Valley, Qinghai-Tibet Plateau

NASA Astrophysics Data System (ADS)

Zhou, Na; Zhang, Chun-Lai; Wu, Xiao-Xu; Wang, Xun-ming; Kang, Li-qiang

2014-11-01

This paper systematically analyzes a valley's aeolian landforms in a semi-humid region and presents a model of its contemporary evolution. Mainling Valley of the Yarlung Zangbo River on the Qinghai-Tibet Plateau was chosen as the case study for the analysis of morphometric characteristics and the evolution sequence of aeolian landforms via field data and remote sensing images. The aeolian landforms were primarily composed of aeolian sand belts on river terraces and dunes (sheets) on hillside slopes. Three types of aeolian sand belts were identified based on their dune types. In type I belts, an erosive air stream combined with relatively high vegetation cover (10%) produced sparsely distributed parabolic dunes with a high variability of dune heights; in type II belts, the continual reworking by the erosive air stream in combination with low vegetation cover (3%) formed more densely distributed barchans and transitional dunes with a moderate variability of dune heights; and in type III belts, the gradual evolution from an erosive sand-laden air stream to a saturated sand-laden air stream in combination with low vegetation cover (2%) produced the densest crescentic dunefields but with the least variability in dune heights. Dune sizes increase, dune shapes become uniform, and dune distribution becomes close from type I to III belts. Lateral linking and merging of the dunes were also observed within the belts. Together this evidence indicates that an evolution sequence may exist. Aeolian dunefields in the belt appear to evolve from embryonic parabolic dunefields to adolescent barchan dunefields and, subsequently, to mature compound crescentic dunefields. As the aeolian sand belt evolves into the mature stage, sand accumulations at the foot of the mountain valley can be steps for sand accumulation on valley-side slopes.

Abrasion by aeolian particles: Earth and Mars

NASA Technical Reports Server (NTRS)

Greeley, R.; Marshall, J. R.; White, B. R.; Pollack, J. B.; Marshall, J.; Krinsley, D.

1984-01-01

Estimation of the rate of aeolian abrasion of rocks on Mars requires knowledge of: (1) particle flux, (2) susceptibilities to abrasion of various rocks, and (3) wind frequencies on Mars. Fluxes and susceptibilities for a wide range of conditions were obtained in the laboratory and combined with wind data from the Viking meteorology experiment. Assuming an abundant supply of sand-sized particles, estimated rates range up to 2.1 x 10 to the minus 2 power cm of abrasion per year in the vicinity of Viking Lander 1. This rate is orders of magnitude too great to be in agreement with the inferred age of the surface based on models of impact crater flux. The discrepancy in the estimated rate of abrasion and the presumed old age of the surface cannot be explained easily by changes in climate or exhumation of ancient surfaces. The primary reason is thought to be related to the agents of abrasion. At least some sand-sized (approx. 100 micrometers) grains appear to be present, as inferred from both lander and orbiter observations. High rates of abrasion occur for all experimental cases involving sands of quartz, basalt, or ash. However, previous studies have shown that sand is quickly comminuted to silt- and clay-sized grains in the martian aeolian regime. Experiments also show that these fine grains are electrostatically charged and bond together as sand-sized aggregates. Laboratory simulations of wind abrasion involving aggregates show that at impact velocities capable of destroying sand, aggregates from a protective veneer on the target surface and can give rise to extremely low abrasion rates.

The aeolian wind tunnel

NASA Technical Reports Server (NTRS)

Iversen, J. D.

1991-01-01

The aeolian wind tunnel is a special case of a larger subset of the wind tunnel family which is designed to simulate the atmospheric surface layer winds to small scale (a member of this larger subset is usually called an atmospheric boundary layer wind tunnel or environmental wind tunnel). The atmospheric boundary layer wind tunnel is designed to simulate, as closely as possible, the mean velocity and turbulence that occur naturally in the atmospheric boundary layer (defined as the lowest portion of the atmosphere, of the order of 500 m, in which the winds are most greatly affected by surface roughness and topography). The aeolian wind tunnel is used for two purposes: to simulate the physics of the saltation process and to model at small scale the erosional and depositional processes associated with topographic surface features. For purposes of studying aeolian effects on the surface of Mars and Venus as well as on Earth, the aeolian wind tunnel continues to prove to be a useful tool for estimating wind speeds necessary to move small particles on the three planets as well as to determine the effects of topography on the evolution of aeolian features such as wind streaks and dune patterns.

Spatial differences of aeolian desertification responses to climate in arid Asia

NASA Astrophysics Data System (ADS)

Wang, Xunming; Hua, Ting; Lang, Lili; Ma, Wenyong

2017-01-01

Most areas of arid Asia are covered by aeolian dunes, sand sheets, gravels, and desert steppes, and may jeopardize nearly 350 million people if climate change increases aeolian desertification. Although the aeolian desertification is mainly triggered by climate changes are extensively acknowledged, the responses of aeolian desertification to various climate scenarios are poorly understood. Based on the tight combinations of dune activity index (DAI) trends and of aeolian desertification, here the spatial differences of aeolian desertification responses on various climate scenarios were reported. The analyzed results show that the variations in temperature, precipitation and wind regime have no significant contributions on aeolian desertification in the extremely arid Asia. From the early to blooming periods of vegetation growth, although temperature rise may benefit vegetation growths in some high latitudes and altitudes, the temperature rise may increase aeolian desertification in most arid Asia regions such as Mongolia, West and Central Asia. In arid Asia, although precipitation increases may benefit the rehabilitation, decreases in precipitation is not the key role on aeolian desertification occurrences in extremely arid regions. From the early to blooming periods of vegetation growths, spatial trends of the sensitivity of aeolian desertification to wind regime varied. Generally, at the regional scales there are relative high sensitivities for aeolian desertification to climate changes in the eastern and western regions of arid Asia, and the climate changes may not play important roles on aeolian desertification occurrence in the central regions. The spatial differences of aeolian desertification responses to climate changes indicate various strategies for aeolian desertification combating are needed in different regions of arid Asia.

Sand deposition in shoreline eddies along five Wild and Scenic Rivers, Idaho

USGS Publications Warehouse

Andrews, E.D.; Vincent, K.R.

2007-01-01

Sand bars deposited along the lateral margin of a river channel are frequently a focus of recreational activities. Sand bars are appealing sites on which to camp, picnic, fish and relax because they are relatively flat, soft, non-cohesive sand, free of vegetation and near the water's edge. The lack of vegetation and cohesion make sand bars easily erodible. Without appreciable deposition of new material, number and size of bars through a given reach of river will decline substantially over a period of years. We studied 63 beaches and their associated eddies located throughout 10 selected reaches within the designated Wild and Scenic River sections of the Lochsa, Selway, Middle Fork Clearwater, Middle Fork Salmon and Salmon Rivers in Idaho to determine the relation of beaches to the frequency and magnitude of streamflows that deposit appreciable quantities of sand. At present, these rivers have been altered little, if at all, by flow regulation, and only the Salmon River has substantial diversion upstream of a study reach. The river reaches studied have an abundance of sand bar beaches of appreciable size, in spite of suspended sand concentrations that rarely exceeded a few hundred milligrams per litre even during the largest floods. Calculated mean annual rates of deposition in an eddy vary from 5.8 to more than 100 cm depending primarily on: (1) the duration of streamflows that inundate the eddy sand bar depositions; (2) the rate of the flow exchange between the channel and an eddy and (3) the concentrations of suspended sand in the primary channel. The annual thickness of sand deposition in an eddy varies greatly from year to year depending on the duration of relatively large streamflows. Maximum annual sand depositions in an eddy are three to nine times the estimated long-term mean values. Relatively large, sustained floods deposit an appreciable portion of total deposition over a period of years. For the period of record, 1930-2002, the seven largest annual

A review of the chronologies and geomorphology of the aeolian landforms in the northwestern Negev dunefield (Israel)

NASA Astrophysics Data System (ADS)

Roskin, Joel

2015-04-01

The northwestern (NW) Negev Desert dunefield covering an area of only 1,300 km2, comprises the eastern end of the northern Sinai Peninsula - NW Negev erg and is probably the most densely dated dune body in the INQUA Dunes Atlas chronologic database. Over 230 luminescence ages (TL, IRSL, and mainly OSL) and radiocarbon dates have been retrieved over the past course of 20 years from calcic and sandy palaeosols serving as dune substrates, sand sheets, vegetated linear dunes (VLDs), fluvial deposits, and archaeological sites. Despite being from different deposit types and aeolian morphologies, and based on different methodologies, the chronologies usually show good compatibility. By reviewing and reassessing the significance of the Eastern Mediterranean INQUA Dunes Atlas chronologies, along with detailed stratigraphic, structural and geomorphologic data and understandings, the major, and possibly extreme, episodes of aeolian activity and stability are outlined. Repetitive chronostratigraphic sequences in VLDs indicate that this dune type, at least in the Negev, comprises a reliable recorder of main dune mobilization periods. This presentation demonstrates that certain combinations of research finds, using different OSL dating strategies and other regional and local late Quaternary records and in particular aeolian ones, are required assets for providing for acceptable local and regional palaeoclimatic interpretations. The distribution of the VLD chronologies points to rapid mobilization during the Heinrich 1 and Younger Dryas, characterized by powerful winds, though VLDs also form in late Holocene palaeoenvironments. Time slices illustrate the different sensitivities of the studied aeolian landforms to the source, availability, and supply of sediment; long- and short-term climate change, local human-induced environmental changes and also their joint effects, that enable evaluation of aeolian responses to future environmental and climate changes.

Tracer techniques in aeolian research: Approaches, applications, and challenges

USDA-ARS?s Scientific Manuscript database

Aeolian processes, the entrainment, transport and deposition of sediments by wind, impacts climate, biogeochemical cycles, food security, environmental quality and human health. Considering the multitude of interactions between aeolian processes and all the major components of the Earth system, ther...

Rapid anthropogenic response to short-term aeolian-fluvial palaeoenvironmental changes during the Late Pleistocene-Holocene transition in the northern Negev Desert, Israel

NASA Astrophysics Data System (ADS)

Roskin, Joel; Katra, Itzhak; Agha, Nuha; Goring-Morris, A. Nigel; Porat, Naomi; Barzilai, Omry

2014-09-01

Archaeological investigations along Nahal Sekher on the eastern edge of Israel's northwestern Negev Desert dunefield revealed concentrations of Epipalaeolithic campsites associated respectively with ancient water bodies. This study, aimed at better understanding the connections between these camps and the water bodies, is concerned with a cluster of Natufian sites. A comprehensive geomorphological study integrating field mapping, stratigraphic sections, sedimentological analysis and optically stimulated luminescence (OSL) ages was conducted in the vicinity of a recently excavated Natufian campsite of Nahal Sekher VI whose artifacts directly overlay aeolian sand dated by OSL to 12.4 ± 0.7 and 11.7 ± 0.5 ka. Residual sequences of diagnostic silty sediments, defined here as low-energy fluvial fine-grained deposits (LFFDs), were identified within the drainage system of central Nahal Sekher around the Nahal Sekher VI site. LFFD sections were found to represent both shoreline and mid-water deposits. The thicker mid-water LFFD deposits (15.7 ± 0.7-10.7 ± 0.5 ka) date within the range of the Epipalaeolithic campsites, while the upper and shoreline LFFD units that thin out into the sands adjacent to the Nahal Sekher VI site display slightly younger ages (10.8 ± 0.4 ka-7.6 ± 0.4 ka). LFFD sedimentation by low-energy concentrated flow and standing-water developed as a result of proximal downstream dune-damming. These water bodies developed as a result of encroaching sand that initially crossed central Nahal Sekher by 15.7 ± 0.7 ka and probably intermittently blocked the course of the wadi. LFFD deposition was therefore a response to a unique combination of regional sand supply due to frequent powerful winds and does not represent climate change in the form of increased precipitation or temperature change. The chronostratigraphies affiliate the Natufian sites to the adjacent ancient water bodies. These relations reflect a rapid, but temporary anthropogenic response to a

Aeolian processes and the bioshpere: Interactions and feedback loops

USDA-ARS?s Scientific Manuscript database

Aeolian processes affect landform evolution, biogeochemical cycles, regional climate, human health, and desertification. The entrainment, transport and deposition of aeolian sediments are recognized as major drivers in the dynamics of the earth system and there is a growing interest in the scientif...

Nonlinear dynamics of Aeolian sand ripples.

PubMed

Prigozhin, L

1999-07-01

We study the initial instability of flat sand surface and further nonlinear dynamics of wind ripples. The proposed continuous model of ripple formation allowed us to simulate the development of a typical asymmetric ripple shape and the evolution of a sand ripple pattern. We suggest that this evolution occurs via ripple merger preceded by several soliton-like interaction of ripples.

Applicability of Unmanned Aerial Vehicles in Research on Aeolian Processes

NASA Astrophysics Data System (ADS)

Algimantas, Česnulevičius; Artūras, Bautrėnas; Linas, Bevainis; Donatas, Ovodas; Kęstutis, Papšys

2018-02-01

Surface dynamics and instabilities are characteristic of aeolian formation. The method of surface comparison is regarded as the most appropriate one for evaluation of the intensity of aeolian processes and the amount of transported sand. The data for surface comparison can be collected by topographic survey measurements and using unmanned aerial vehicles. Time cost for relief microform fixation and measurement executing topographic survey are very high. The method of unmanned aircraft aerial photographs fixation also encounters difficulties because there are no stable clear objects and contours that enable to link aerial photographs, to determine the boundaries of captured territory and to ensure the accuracy of surface measurements. Creation of stationary anchor points is irrational due to intense sand accumulation and deflation in different climate seasons. In September 2015 and in April 2016 the combined methodology was applied for evaluation of intensity of aeolian processes in the Curonian Spit. Temporary signs (marks) were installed on the surface, coordinates of the marks were fixed using GPS and then flight of unmanned aircraft was conducted. The fixed coordinates of marks ensure the accuracy of measuring aerial imagery and the ability to calculate the possible corrections. This method was used to track and measure very small (micro-rank) relief forms (5-10 cm height and 10-20 cm length). Using this method morphometric indicators of micro-terraces caused by sand dunes pressure to gytia layer were measured in a non-contact way. An additional advantage of the method is the ability to accurately link the repeated measurements. The comparison of 3D terrain models showed sand deflation and accumulation areas and quantitative changes in the terrain very clearly.

Conditions and processes affecting sand resources at archeological sites in the Colorado River corridor below Glen Canyon Dam, Arizona

USGS Publications Warehouse

East, Amy E.; Collins, Brian D.; Sankey, Joel B.; Corbett, Skye C.; Fairley, Helen C.; Caster, Joshua J.

2016-05-17

We conclude that most of the river-corridor archeological sites are at elevated risk of net erosion under present dam operations. In the present flow regime, controlled floods do not simulate the magnitude or frequency of natural floods, and are not large enough to deposit sand at elevations that were flooded at annual to decadal intervals in predam time. For archeological sites that depend upon river-derived sand, we infer elevated erosion risk owing to a combination of reduced sand supply (both fluvial and aeolian) through (1) the lower-than-natural flood magnitude, frequency, and sediment supply of the controlled-flooding protocol; (2) reduction of open, dry sand area available for wind redistribution under current normal (nonflood) dam operations, which do not include flows as low as natural seasonal low flows and do include substantial daily flow fluctuations; and (3) impeded aeolian sand entrainment and transport owing to increased riparian vegetation growth in the absence of larger, more-frequent floods. If dam operations were to increase the supply of sand available for windblown transport—for example, through larger floods, sediment augmentation, or increased fluvial sandbar exposure by low flows—and also decrease riparian vegetation, the prevalence of active aeolian sand could increase over time, and the propensity for unmitigated gully erosion could decrease. Although the evolution of river-corridor landscapes and archeological sites has been altered fundamentally by the lack of large, sediment-rich floods (flows on the order of 5,000 m3/s), some combination of sediment-rich flows above 1,270 m3/s, seasonal flows below 226 m3/s, and riparian-vegetation removal might increase the preservation potential for sand-dependent archeological resources in the Colorado River corridor.

A Wireless Sensor Network for the Real-Time Remote Measurement of Aeolian Sand Transport on Sandy Beaches and Dunes

PubMed Central

Cappelli, Irene; Mecocci, Alessandro; Alquini, Fernanda

2018-01-01

Direct measurements of aeolian sand transport on coastal dunes and beaches is of paramount importance to make correct decisions about coast management. As most of the existing studies are mainly based on a statistical approach, the solution presented in this paper proposes a sensing structure able to orient itself according to wind direction and directly calculate the amount of wind-transported sand by collecting it and by measuring its weight. Measurements are performed remotely without requiring human action because the structure is equipped with a ZigBee radio module, which periodically sends readings to a local gateway. Here data are processed by a microcontroller and then transferred to a remote data collection centre, through GSM technology. The ease of installation, the reduced power consumption and the low maintenance required, make the proposed solution able to work independently, limiting human intervention, for all the duration of the expected experimental campaign. In order to analyze the cause-effect relationship between the transported sand and the wind, the sensing structure is integrated with a multi-layer anemoscope-anemometer structure. The overall sensor network has been developed and tested in the laboratory, and its operation has been validated in field through a 48 h measurement campaign. PMID:29518060

A Wireless Sensor Network for the Real-Time Remote Measurement of Aeolian Sand Transport on Sandy Beaches and Dunes.

PubMed

Pozzebon, Alessandro; Cappelli, Irene; Mecocci, Alessandro; Bertoni, Duccio; Sarti, Giovanni; Alquini, Fernanda

2018-03-08

Direct measurements of aeolian sand transport on coastal dunes and beaches is of paramount importance to make correct decisions about coast management. As most of the existing studies are mainly based on a statistical approach, the solution presented in this paper proposes a sensing structure able to orient itself according to wind direction and directly calculate the amount of wind-transported sand by collecting it and by measuring its weight. Measurements are performed remotely without requiring human action because the structure is equipped with a ZigBee radio module, which periodically sends readings to a local gateway. Here data are processed by a microcontroller and then transferred to a remote data collection centre, through GSM technology. The ease of installation, the reduced power consumption and the low maintenance required, make the proposed solution able to work independently, limiting human intervention, for all the duration of the expected experimental campaign. In order to analyze the cause-effect relationship between the transported sand and the wind, the sensing structure is integrated with a multi-layer anemoscope-anemometer structure. The overall sensor network has been developed and tested in the laboratory, and its operation has been validated in field through a 48 h measurement campaign.

Spatial and temporal variations of aeolian sediment input to the tributaries (the Ten Kongduis) of the upper Yellow River

NASA Astrophysics Data System (ADS)

Yang, Hui; Shi, Changxing

2018-02-01

The Ten Kongduis of the upper Yellow River, located in Inner Mongolia, northern China, is an area with active wind-water coupled erosion and hence one of the main sediment sources of the Yellow River. In this study, we analyzed the characteristics of spatial and temporal variations of aeolian sediment input to the river channel. For this purpose, three segments of sand dune-covered banks of the Maobula and the Xiliugou kongduis were investigated three times from November 2014 to November 2015 using a 3-D laser scanner, and the displacement of banks of desert reaches of three kongduis was derived from interpreting remote sensing images taking in the years from 2005 to 2015. The data of the surveyed sand dunes reveal that the middle kongduis were fed by aeolian sand through the sand dunes moving towards the river channels. The amount of aeolian sediment input was estimated to be about 14.94 × 104 t/yr in the Maobula Kongdui and about 5.76 × 104 t/yr in the Xiliugou Kongdui during the period from November 2014 to November 2015. According to the interpretation results of remote sensing images, the amount of aeolian sediment input to the Maobula Kongdui was about 15.74 × 104 t in 2011 and 18.2 × 104 t in 2012. In the Xiliugou Kongdui, it was in the range of 9.52 × 104 - 9.99 × 104 t in 2012 and in the springs of 2013 and 2015. In the Hantaichuan Kongdui, it was 7.04 × 104 t in 2012, 7.53 × 104 t in the spring of 2013, and 8.52 × 104 t in the spring of 2015. Owing to the changes in wind and rainfall, both interseasonal and interannual sediment storage and release mechanisms exist in the processes of aeolian sand being delivered into the kongduis. However, all of the aeolian sediment input to the Ten Kongduis should be delivered downstream by the river flows during a long term.

Recent Aeolian Dune Change on Mars

NASA Technical Reports Server (NTRS)

Bourke, M. C.; Edgett, K. S.; Cantor, B. A.

2007-01-01

Previous comparisons of Martian aeolian dunes in satellite images have not detected any change in dune form or position. Here, we show dome dunes in the north polar region that shrank and then disappeared over a period of 3.04 Mars years (5.7 Earth years), while larger, neighboring dunes showed no erosion or movement. The removal of sand from these dunes indicates that not only is the threshold wind speed for saltation exceeded under present conditions on Mars, but that any sand that is available for transport is likely to be moved. Dunes that show no evidence of change could be crusted, indurated. or subject to infrequent episodes of movement.

Analyzing the Sand-fixing Effect of Feldspathic Sandstone from the Texture Characteristics

NASA Astrophysics Data System (ADS)

Zhang, lu; Ban, Jichang

2018-01-01

The purpose of this research was aimed to study the sand fixing effect of feldspathic sandstone in Mu Us Sandy Land, to provide a scienticic basis for desertification control, soil and water conservation and development of farming there. Methods of mixing feldspathic sandstone and aeolian sandy soil according to 1: 0, 1: 1, 1: 2, 1: 5, and 0: 1 mass ratioes, the graded composition and characteristics were studied with laser particle size analyzer. The result showed that these features of sand-based, loosely structured, easy to wind erosion of aeolian sandy soil were changed before feldspathic sandstone and aeolian sandy soil compounding. The <0.05 mm particle mass increased with feldspathic sandstone mass increasing. The texture presented this kind of change from sand to sandy loam to loam to silt loam. The small particle size distribution, good homogeneity and other features of aeolian sandy soil were improved to a certain degree, and the particle size distribution became broad before feldspathic sandstone and aeolian sandy soil compounding. The particle grading was continuous, and the grading characteristic was good when m(F): m(S) was 1: 5(Cu was 54.71 and Cc was 2.54) or when m(F): m(S) was 1: 2(Cu was 76.21, Cc was 1.12). The conclusion is that feldspathic sandstone has sand-fixing effect in texture characteristics, which heightens with feldspathic sandstone mass increasing, and when the mass ratio of feldspathic sandstone: aeolian sandy soil is 1: 2 or 1: 5 which compound better.

Tectonic and climatic controls on continental depositional facies in the Karoo Basin of northern Natal, South Africa

NASA Astrophysics Data System (ADS)

Turner, Brian R.

1986-02-01

The eastern Karoo Basin, South Africa, contains a thick sequence of terrigenous clastic sediments comprising a meanderbelt facies, braided channel facies divided into coarse and fine subfacies, fluviolacustrine facies and aeolian facies. Depositional trends and changes in fluvial style reflect a progressive increase in aridity of the climate under stable tectonic conditions, interrupted by two phases of source area tectonism and the development of fine and coarse clastic wedges of the braided channel subfacies; the latter signifying a short interlude of cool, wet conditions. The fine braided channel subfacies occurs in the upper part of the meanderbelt facies, which was deposited by ephemeral, meandering mixed-load streams of variable discharge and sinuosity, under dry, semi-arid climatic conditions. These deposited complex, internally discordant channel sands and well-developed levee deposits. Following deposition of the coarse braided channel subfacies semi-arid conditions returned and fluvial deposition was dominated by ephemeral, straight to slightly sinuous mixed load streams characterised by simple channel sand bodies. As the aridity of the climate increased, the streams became more localised and carried an increasing proportion of fines. Interbedded with and overlying the fluvial deposits is a mudstone-dominated lacustrine sequence grading up into aeolian sands suggesting a playa lake-type situation. The general absence of evaporites from these sediments is attributed to the fresh nature of the lake waters, as evidenced by the freshwater aquatic organisms and clay-mineral suite, the lack of adequate inflow for solute accumulation and the removal of dust impregnated by salts from the surface of the dry lake bed during the dry season by superheated, upward-spiralling columns of air. Broadly similar environments to the fluvio-lacustrine and aeolian facies sequence are to be found in the Lake Eyre Basin of central Australia and the Okavango "delta" of northern

High-frequency measurements of aeolian saltation flux: Field-based methodology and applications

NASA Astrophysics Data System (ADS)

Martin, Raleigh L.; Kok, Jasper F.; Hugenholtz, Chris H.; Barchyn, Thomas E.; Chamecki, Marcelo; Ellis, Jean T.

2018-02-01

Aeolian transport of sand and dust is driven by turbulent winds that fluctuate over a broad range of temporal and spatial scales. However, commonly used aeolian transport models do not explicitly account for such fluctuations, likely contributing to substantial discrepancies between models and measurements. Underlying this problem is the absence of accurate sand flux measurements at the short time scales at which wind speed fluctuates. Here, we draw on extensive field measurements of aeolian saltation to develop a methodology for generating high-frequency (up to 25 Hz) time series of total (vertically-integrated) saltation flux, namely by calibrating high-frequency (HF) particle counts to low-frequency (LF) flux measurements. The methodology follows four steps: (1) fit exponential curves to vertical profiles of saltation flux from LF saltation traps, (2) determine empirical calibration factors through comparison of LF exponential fits to HF number counts over concurrent time intervals, (3) apply these calibration factors to subsamples of the saltation count time series to obtain HF height-specific saltation fluxes, and (4) aggregate the calibrated HF height-specific saltation fluxes into estimates of total saltation fluxes. When coupled to high-frequency measurements of wind velocity, this methodology offers new opportunities for understanding how aeolian saltation dynamics respond to variability in driving winds over time scales from tens of milliseconds to days.

Regional aeolian dynamics and sand mixing in the Gran Desierto - Evidence from Landsat Thematic Mapper images

NASA Technical Reports Server (NTRS)

Blount, Grady; Greeley, Ronald; Christensen, Phillip R.; Smith, Milton O.; Adams, John B.

1990-01-01

Mesoscale mapping of spatial variations in sand composition of the Gran Desierto (Sonora, Mexico) was carried out on multispectral Landsat TM images of this region, making it possible to examine the dynamic development of sand sheets and dunes. Compositions determined from remote imagery were found to agree well with samples from selected areas. The sand populations delineated were used to describe the sediment source areas, transport paths, and deposition sites. The image analysis revealed important compositional variations aver large areas that were not readily apparent in the field data.

Terrestrial sensitivity to abrupt cooling recorded by aeolian activity in northwest Ohio, USA

USGS Publications Warehouse

Campbell, M.C.; Fisher, T.G.; Goble, R.J.

2011-01-01

Optically stimulated luminescence dated sand dunes and Pleistocene beach ridges in northwest Ohio are used to reconstruct landscape modification more than 5000. yr after deglaciation. Four of the OSL ages (13.3-11.1. ka) cluster around the Younger Dryas cold event, five ages (10.8-8.2. ka) cluster around the Preboreal, one young age (0.9-0.7. ka) records more recent aeolian activity, and one age of 15.1-13.1. ka dates a barrier spit in Lake Warren. In northwest Ohio, both landscape instability recorded by aeolian activity and a vegetation response recorded by pollen are coeval with the Younger Dryas. However, the climate conditions during the Preboreal resulting in aeolian activity are not recorded in the available pollen records. From this, we conclude that aeolian dunes and surfaces susceptible to deflation are sensitive to cooler, drier episodes of climate and can complement pollen data. Younger Dryas and Preboreal aged aeolian activity in northwestern Ohio coincides with aeolian records elsewhere in the Great Lakes region east of the prairie-forest ecotone. ?? 2011 University of Washington.

Aeolian sand as a tool for understanding Mars: Thermal infrared remote sensing of volcaniclastic Mars-analog sand dunes in Christmas Lake Valley, Oregon, U.S.A.

NASA Astrophysics Data System (ADS)

Edgett, Kenneth S.

1996-10-01

INTRODUCTION: On Earth, aeolian sand dunes are used as tools of scientific inquiry. Holocene and Pleistocene dunes preserve clues about Quaternary climate variations and human activities ranging from Ice Age hunting practices to Twentieth Century warfare. Modern dunes contain the sedimentary textures and structures necessary for interpreting ancient sandstones, and they provide natural laboratories for investigation of aeolian physics and desertification processes. The dunes of Mars can likewise be used as scientific tools. Dunes provide relatively dust-free surfaces. From a remote sensing perspective, martian dunes have much potential for providing clues about surface mineralogy and the interaction between the surface and atmosphere. Such information can in turn provide insights regarding crust composition, volcanic evolution, present and past climate events, and perhaps weathering rates. The Mars Global Surveyor Thermal Emission Spectrometer (TES) is expected to reach the planet in September 1997. TES will provide 6 to 50 micrometer spectra of the martian surface at ground resolutions of 3 to 9 km. Sandy aeolian environments on Mars might provide key information about bedrock composition. To prepare for the TES investigation, I have been examining a thermal infrared image of a Mars-composition analog dune field in Christmas Lake Valley, Oregon. COMPOSITION AND GEOLOGIC SETTING: The "Shifting Sand Dunes" dune field is located at the eastern end of Christmas Lake Valley, in what was once the Pleistocene Fort Rock Lake [1]. Much of the sand that makes up the Shifting Sand Dunes dune field is reworked Mt. Mazama airfall from its terminal eruption 6,800 years ago, plus material deflated from the lake bed [1, 2]. The main constituents of the dunes are volcanic glass and devitrified glass fragments, plagioclase crystals, basalt lithic fragments, aggregates of silt and clay-size volcanic ash, pyroxenes, opaque oxide minerals (mostly magnetite), and trace occurrences of

Hydrogeology of sand and gravel deposits near Nepaug Reservoir, New Hartford and Burlington, Connecticut

USGS Publications Warehouse

Stone, Janet Radway; Starn, J. Jeffrey; Morrison, Jonathan

2001-01-01

Sand and gravel deposits near the Nepaug Reservoir in New Hartford and Burlington, Connecticut, were studied to provide a basis for ongoing investigations that will evaluate water-quality conditions in the watershed and the effects of sand and gravel mining on the quality of water in the reservoir. In the Nepaug area, surficial glacial materials overlie crystalline bedrock that is predominantly schist and gneiss. Along the western side of Nepaug Reservoir, glacial stratified deposits were laid down as ice-marginal deltas in a series of small glacial lakes that formed sequentially as the ice margin retreated northeastward through the area. These deposits are as much as 250 feet thick and are subdivided into coarse-grained units (gravel, sand and gravel, and sand deposits) and fine-grained units (very fine sand, silt, and clay deposits). Approximately 954 million cubic feet of sand and gravel is contained in four delineated deposits in two areas near the reservoir. The sand and gravel deposits adjacent to the Nepaug Reservoir can affect the physical and chemical responses of the watershed. Removal of the sand and gravel would likely result in increased streamflow peaks associated with storms and decreased streamflow during low-flow periods. Streamflow during floods and droughts at Burlington Brook and Clear Brook, a tributary to the Nepaug Reservoir, were compared to determine how the volume of sand and gravel in a watershed affects ground-water storage and the way water is released from storage. Removal of unsaturated deposits also may affect chemical interactions between water and sediment and cause changes in the amount of dissolved constituents in the water.

Basaltic lava flows covering active aeolian dunes in the Paraná Basin in southern Brazil: Features and emplacement aspects

NASA Astrophysics Data System (ADS)

Waichel, Breno L.; Scherer, Claiton M. S.; Frank, Heinrich T.

2008-03-01

Burial of active aeolian dunes by lava flows can preserve the morphology of the dunes and generate diverse features related to interaction between unconsolidated sediments and lavas. In the study area, located in southern Brazil, burial of aeolian deposits by Cretaceous basaltic lava flows completely preserved dunes, and generate sand-deformation features, sand diapirs and peperite-like breccia. The preserved dunes are crescentic and linear at the main contact with basalts, and smaller crescentic where interlayered with lavas. The various feature types formed on sediment surfaces by the advance of the flows reflect the emplacement style of the lavas which are compound pahoehoe type. Four feature types can be recognized: (a) type 1 features are related to the advance of sheet flows in dune-interdune areas with slopes > 5°, (b) type 2 is formed where the lava flows advance in lobes and climb the stoss slope of crescentic dunes (slopes 8-12°), (c) type 3 is generated by toes that descend the face of linear dunes (slopes 17-23°) and (d) type 4 occurs when lava lobes descend the stoss slope of crescentic dunes (slopes 10-15°). The direction of the flows, the disposition and morphology of the dunes and the ground slope are the main factors controlling formation of the features. The injection of unconsolidated sand in lava lobes forms diapirs and peperite-like breccias. Sand diapirs occur at the basal portion of lobes where the lava was more solidified. Peperite-like breccias occur in the inner portion where lava was more plastic, favoring the mingling of the components. The generation of both features is related to a mechanical process: the weight of the lava causes the injection of sand into the lava and the warming of the air in the pores of the sand facilitates this process. The lava-sediment interaction features presented here are consistent with previous reports of basalt lavas with unconsolidated arid sediments, and additional new sand-deformation features

Holocene aeolian activity in the Gonghe Basin, north-eastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Stauch, Georg; Lai, Zhongping; Lehmkuhl, Frank; Schulte, Philipp

2016-04-01

The Gonghe Basin is located on the north-eastern edge of Tibetan Plateau and has a mean altitude of 3000 m asl. With a size of 20.000 km² it is the largest intramontane Basin on the north-eastern Plateau. The well-studied Qinghai Basin is situated north of the Basin, while the drier central Plateau is further south-west. Previous research indicated an early onset of the aeolian accumulation in the Qinghai Basin at around 18 ka while in the areas further to the south-west aeolian archives date back only to the beginning of the Holocene. First new OSL ages from aeolian sand and loess indicate a intermediate timing of the aeolian accumulation in the Gonghe Basin at the transition from the late glacial to the Holocene. Late glacial and early Holocene ages of aeolian sediments were hitherto associated with wetter climate conditions caused by the strengthening of the Asian summer monsoon. Higher moisture availability resulted in an increased vegetation cover, leading to the permanent stabilization of the aeolian sediments. Under glacial climate conditions a constant remobilization of the sediments can be assumed. The new OSL ages from the Gonghe Basin indicate a progressive shift of the monsoonal strength in westward directions during the late glacial until the early Holocene.

Sedimentology and palaeontology of upper Karoo aeolian strata (Early Jurassic) in the Tuli Basin, South Africa

NASA Astrophysics Data System (ADS)

Bordy, Emese M.; Catuneanu, Octavian

2002-08-01

The Karoo Supergroup in the Tuli Basin (South Africa) consists of a sedimentary sequence composed of four stratigraphic units, namely the Basal, Middle and Upper units, and Clarens Formation. The units were deposited in continental settings from approximately Late Carboniferous to Middle Jurassic. This paper focuses on the Clarens Formation, which was examined in terms of sedimentary facies and palaeo-environments based on evidence provided by primary sedimentary structures, palaeo-flow measurements and palaeontological findings. Two main facies associations have been identified: (i) massive and large-scale planar cross-bedded sandstones of aeolian origin; and (ii) horizontally and cross-stratified sandstones of fluvial origin. Most of the sandstone lithofacies of the Clarens Formation were generated as transverse aeolian dunes produced by northwesterly winds in a relatively wet erg milieu. Direct evidence of aquatic subenvironments comes from local small ephemeral stream deposits, whereas palaeontological data provide indirect evidence. Fossils of the Clarens Formation include petrified logs of Agathoxylon sp. wood type and several trace fossils which were produced by insects and vertebrates. The upper part of the Clarens Formation lacks both direct and indirect evidence of aquatic conditions, and this suggests aridification that led to the dominance of dry sand sea conditions.

Observations of an aeolian landscape: From surface to orbit in Gale Crater

NASA Astrophysics Data System (ADS)

Day, Mackenzie; Kocurek, Gary

2016-12-01

Landscapes derived solely from aeolian processes are rare on Earth because of the dominance of subaqueous processes. In contrast, aeolian-derived landscapes should typify Mars because of the absence of liquid water, the long exposure times of surfaces, and the presence of wind as the default geomorphic agent. Using the full range of available orbital and Mars Science Laboratory rover Curiosity images, wind-formed features in Gale Crater were cataloged and analyzed in order to characterize the aeolian landscape and to derive the evolution of the crater wind regime over time. Inferred wind directions show a dominance of regional northerly winds over geologic time-scales, but a dominance of topography-driven katabatic winds in modern times. Landscapes in Gale Crater show a preponderance of aeolian features at all spatial scales. Interpreted processes forming these features include first-cycle aeolian abrasion of bedrock, pervasive deflation, organization of available sand into bedforms, abundant cratering, and gravity-driven wasting, all of which occur over a background of slow physical weathering. The observed landscapes are proposed to represent a spectrum of progressive surface denudation from fractured bedrock, to retreating bedrock-capped mesas, to remnant hills capped by bedrock rubble, to desert pavement plains. This model of landscape evolution provides the mechanism by which northerly winds acting over ∼3 Ga excavated tens of thousands of cubic kilometers of material from the once sediment-filled crater, thus carving the intra-crater moat and exhuming Mount Sharp (Aeolis Mons). The current crater surface is relatively sand-starved, indicating that potential sediment deflation from the crater is greater than sediment production, and that most exhumation of Mount Sharp occurred in the ancient geologic past.

Crater relaxation on Titan aided by low thermal conductivity sand infill

NASA Astrophysics Data System (ADS)

Schurmeier, Lauren R.; Dombard, Andrew J.

2018-05-01

Titan's few impact craters are currently many hundreds of meters shallower than the depths expected. Assuming these craters initially had depths equal to that of similar-size fresh craters on Ganymede and Callisto (moons of similar size, composition, and target lithology), then some process has shallowed them over time. Since nearly all of Titan's recognized craters are located within the arid equatorial sand seas of organic-rich dunes, where rain is infrequent, and atmospheric sedimentation is expected to be low, it has been suggested that aeolian infill plays a major role in shallowing the craters. Topographic relaxation at Titan's current heat flow was previously assumed to be an unimportant process on Titan due to its low surface temperature (94 K). However, our estimate of the thermal conductivity of Titan's organic-rich sand is remarkably low (0.025 W m-1 K-1), and when in thick deposits, will result in a thermal blanketing effect that can aid relaxation. Here, we simulate the relaxation of Titan's craters Afekan, Soi, and Sinlap including thermal effects of various amounts of sand inside and around Titan's craters. We find that the combination of aeolian infill and subsequent relaxation can produce the current crater depths in a geologically reasonable period of time using Titan's current heat flow. Instead of needing to fill completely the missing volume with 100% sand, only ∼62%, ∼71%, and ∼97%, of the volume need be sand at the current basal heat flux for Afekan, Soi, and Sinlap, respectively. We conclude that both processes are likely at work shallowing these craters, and this finding contributes to why Titan overall lacks impact craters in the arid equatorial regions.

Effects of aeolian erosion on microbial release from solids.

NASA Technical Reports Server (NTRS)

Gustan, E. A.; Olson, R. L.; Taylor, D. M.; Green, R. H.

1972-01-01

This study was initiated to determine the percentage of spores that would be expected to be released from the interior of solid materials by aeolian erosion on a planetary surface. Methyl methacrylate and Eccobond disks were fabricated so that each disk contained approximately 40,000 Bacillus subtilis var. niger spores. The disks were placed in a specially designed sandblasting device and eroded. Exposure periods of 0.5, 2 and 24 hours were investigated using filtered air to accelerate the sand. A series of tests was also conducted for a 0.5 hour period using carbon dioxide. Examination of the erosion products showed that less than 1% of the spores originally contained in the solids was released by aeolian erosion.

Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars

PubMed Central

Stern, Jennifer C.; Sutter, Brad; Freissinet, Caroline; Navarro-González, Rafael; McKay, Christopher P.; Archer, P. Douglas; Buch, Arnaud; Brunner, Anna E.; Coll, Patrice; Eigenbrode, Jennifer L.; Fairen, Alberto G.; Franz, Heather B.; Glavin, Daniel P.; Kashyap, Srishti; McAdam, Amy C.; Ming, Douglas W.; Steele, Andrew; Szopa, Cyril; Wray, James J.; Martín-Torres, F. Javier; Zorzano, Maria-Paz; Conrad, Pamela G.; Mahaffy, Paul R.; Kemppinen, Osku; Bridges, Nathan; Johnson, Jeffrey R.; Minitti, Michelle; Cremers, David; Bell, James F.; Edgar, Lauren; Farmer, Jack; Godber, Austin; Wadhwa, Meenakshi; Wellington, Danika; McEwan, Ian; Newman, Claire; Richardson, Mark; Charpentier, Antoine; Peret, Laurent; King, Penelope; Blank, Jennifer; Weigle, Gerald; Schmidt, Mariek; Li, Shuai; Milliken, Ralph; Robertson, Kevin; Sun, Vivian; Baker, Michael; Edwards, Christopher; Ehlmann, Bethany; Farley, Kenneth; Griffes, Jennifer; Grotzinger, John; Miller, Hayden; Newcombe, Megan; Pilorget, Cedric; Rice, Melissa; Siebach, Kirsten; Stack, Katie; Stolper, Edward; Brunet, Claude; Hipkin, Victoria; Léveillé, Richard; Marchand, Geneviève; Sánchez, Pablo Sobrón; Favot, Laurent; Cody, George; Steele, Andrew; Flückiger, Lorenzo; Lees, David; Nefian, Ara; Martin, Mildred; Gailhanou, Marc; Westall, Frances; Israël, Guy; Agard, Christophe; Baroukh, Julien; Donny, Christophe; Gaboriaud, Alain; Guillemot, Philippe; Lafaille, Vivian; Lorigny, Eric; Paillet, Alexis; Pérez, René; Saccoccio, Muriel; Yana, Charles; Armiens-Aparicio, Carlos; Rodríguez, Javier Caride; Blázquez, Isaías Carrasco; Gómez, Felipe Gómez; Gómez-Elvira, Javier; Hettrich, Sebastian; Malvitte, Alain Lepinette; Jiménez, Mercedes Marín; Martínez-Frías, Jesús; Martín-Soler, Javier; - Torres, F. Javier Martín; Jurado, Antonio Molina; Mora-Sotomayor, Luis; Caro, Guillermo Muñoz; López, Sara Navarro; Peinado-González, Verónica; Pla-García, Jorge; Manfredi, José Antonio Rodriguez; Romeral-Planelló, Julio José; Fuentes, Sara Alejandra Sans; Martinez, Eduardo Sebastian; Redondo, Josefina Torres; Urqui-O'Callaghan, Roser; Mier, María-Paz Zorzano; Chipera, Steve; Lacour, Jean-Luc; Mauchien, Patrick; Sirven, Jean-Baptiste; Manning, Heidi; Fairén, Alberto; Hayes, Alexander; Joseph, Jonathan; Squyres, Steven; Sullivan, Robert; Thomas, Peter; Dupont, Audrey; Lundberg, Angela; Melikechi, Noureddine; Mezzacappa, Alissa; DeMarines, Julia; Grinspoon, David; Reitz, Günther; Prats, Benito; Atlaskin, Evgeny; Genzer, Maria; Harri, Ari-Matti; Haukka, Harri; Kahanpää, Henrik; Kauhanen, Janne; Kemppinen, Osku; Paton, Mark; Polkko, Jouni; Schmidt, Walter; Siili, Tero; Fabre, Cécile; Wray, James; Wilhelm, Mary Beth; Poitrasson, Franck; Patel, Kiran; Gorevan, Stephen; Indyk, Stephen; Paulsen, Gale; Gupta, Sanjeev; Bish, David; Schieber, Juergen; Gondet, Brigitte; Langevin, Yves; Geffroy, Claude; Baratoux, David; Berger, Gilles; Cros, Alain; d’Uston, Claude; Forni, Olivier; Gasnault, Olivier; Lasue, Jérémie; Lee, Qiu-Mei; Maurice, Sylvestre; Meslin, Pierre-Yves; Pallier, Etienne; Parot, Yann; Pinet, Patrick; Schröder, Susanne; Toplis, Mike; Lewin, Éric; Brunner, Will; Heydari, Ezat; Achilles, Cherie; Oehler, Dorothy; Sutter, Brad; Cabane, Michel; Coscia, David; Israël, Guy; Szopa, Cyril; Dromart, Gilles; Robert, François; Sautter, Violaine; Le Mouélic, Stéphane; Mangold, Nicolas; Nachon, Marion; Buch, Arnaud; Stalport, Fabien; Coll, Patrice; François, Pascaline; Raulin, François; Teinturier, Samuel; Cameron, James; Clegg, Sam; Cousin, Agnès; DeLapp, Dorothea; Dingler, Robert; Jackson, Ryan Steele; Johnstone, Stephen; Lanza, Nina; Little, Cynthia; Nelson, Tony; Wiens, Roger C.; Williams, Richard B.; Jones, Andrea; Kirkland, Laurel; Treiman, Allan; Baker, Burt; Cantor, Bruce; Caplinger, Michael; Davis, Scott; Duston, Brian; Edgett, Kenneth; Fay, Donald; Hardgrove, Craig; Harker, David; Herrera, Paul; Jensen, Elsa; Kennedy, Megan R.; Krezoski, Gillian; Krysak, Daniel; Lipkaman, Leslie; Malin, Michael; McCartney, Elaina; McNair, Sean; Nixon, Brian; Posiolova, Liliya; Ravine, Michael; Salamon, Andrew; Saper, Lee; Stoiber, Kevin; Supulver, Kimberley; Van Beek, Jason; Van Beek, Tessa; Zimdar, Robert; French, Katherine Louise; Iagnemma, Karl; Miller, Kristen; Summons, Roger; Goesmann, Fred; Goetz, Walter; Hviid, Stubbe; Johnson, Micah; Lefavor, Matthew; Lyness, Eric; Breves, Elly; Dyar, M. Darby; Fassett, Caleb; Blake, David F.; Bristow, Thomas; DesMarais, David; Edwards, Laurence; Haberle, Robert; Hoehler, Tori; Hollingsworth, Jeff; Kahre, Melinda; Keely, Leslie; McKay, Christopher; Wilhelm, Mary Beth; Bleacher, Lora; Brinckerhoff, William; Choi, David; Conrad, Pamela; Dworkin, Jason P.; Eigenbrode, Jennifer; Floyd, Melissa; Freissinet, Caroline; Garvin, James; Glavin, Daniel; Harpold, Daniel; Jones, Andrea; Mahaffy, Paul; Martin, David K.; McAdam, Amy; Pavlov, Alexander; Raaen, Eric; Smith, Michael D.; Stern, Jennifer; Tan, Florence; Trainer, Melissa; Meyer, Michael; Posner, Arik; Voytek, Mary; Anderson, Robert C; Aubrey, Andrew; Beegle, Luther W.; Behar, Alberto; Blaney, Diana; Brinza, David; Calef, Fred; Christensen, Lance; Crisp, Joy A.; DeFlores, Lauren; Ehlmann, Bethany; Feldman, Jason; Feldman, Sabrina; Flesch, Gregory; Hurowitz, Joel; Jun, Insoo; Keymeulen, Didier; Maki, Justin; Mischna, Michael; Morookian, John Michael; Parker, Timothy; Pavri, Betina; Schoppers, Marcel; Sengstacken, Aaron; Simmonds, John J.; Spanovich, Nicole; Juarez, Manuel de la Torre; Vasavada, Ashwin R.; Webster, Christopher R.; Yen, Albert; Archer, Paul Douglas; Cucinotta, Francis; Jones, John H.; Ming, Douglas; Morris, Richard V.; Niles, Paul; Rampe, Elizabeth; Nolan, Thomas; Fisk, Martin; Radziemski, Leon; Barraclough, Bruce; Bender, Steve; Berman, Daniel; Dobrea, Eldar Noe; Tokar, Robert; Vaniman, David; Williams, Rebecca M. E.; Yingst, Aileen; Lewis, Kevin; Leshin, Laurie; Cleghorn, Timothy; Huntress, Wesley; Manhès, Gérard; Hudgins, Judy; Olson, Timothy; Stewart, Noel; Sarrazin, Philippe; Grant, John; Vicenzi, Edward; Wilson, Sharon A.; Bullock, Mark; Ehresmann, Bent; Hamilton, Victoria; Hassler, Donald; Peterson, Joseph; Rafkin, Scot; Zeitlin, Cary; Fedosov, Fedor; Golovin, Dmitry; Karpushkina, Natalya; Kozyrev, Alexander; Litvak, Maxim; Malakhov, Alexey; Mitrofanov, Igor; Mokrousov, Maxim; Nikiforov, Sergey; Prokhorov, Vasily; Sanin, Anton; Tretyakov, Vladislav; Varenikov, Alexey; Vostrukhin, Andrey; Kuzmin, Ruslan; Clark, Benton; Wolff, Michael; McLennan, Scott; Botta, Oliver; Drake, Darrell; Bean, Keri; Lemmon, Mark; Schwenzer, Susanne P.; Anderson, Ryan B.; Herkenhoff, Kenneth; Lee, Ella Mae; Sucharski, Robert; Hernández, Miguel Ángel de Pablo; Ávalos, Juan José Blanco; Ramos, Miguel; Kim, Myung-Hee; Malespin, Charles; Plante, Ianik; Muller, Jan-Peter; Navarro-González, Rafael; Ewing, Ryan; Boynton, William; Downs, Robert; Fitzgibbon, Mike; Harshman, Karl; Morrison, Shaunna; Dietrich, William; Kortmann, Onno; Palucis, Marisa; Sumner, Dawn Y.; Williams, Amy; Lugmair, Günter; Wilson, Michael A.; Rubin, David; Jakosky, Bruce; Balic-Zunic, Tonci; Frydenvang, Jens; Jensen, Jaqueline Kløvgaard; Kinch, Kjartan; Koefoed, Asmus; Madsen, Morten Bo; Stipp, Susan Louise Svane; Boyd, Nick; Campbell, John L.; Gellert, Ralf; Perrett, Glynis; Pradler, Irina; VanBommel, Scott; Jacob, Samantha; Owen, Tobias; Rowland, Scott; Atlaskin, Evgeny; Savijärvi, Hannu; Boehm, Eckart; Böttcher, Stephan; Burmeister, Sönke; Guo, Jingnan; Köhler, Jan; García, César Martín; Mueller-Mellin, Reinhold; Wimmer-Schweingruber, Robert; Bridges, John C.; McConnochie, Timothy; Benna, Mehdi; Franz, Heather; Bower, Hannah; Brunner, Anna; Blau, Hannah; Boucher, Thomas; Carmosino, Marco; Atreya, Sushil; Elliott, Harvey; Halleaux, Douglas; Rennó, Nilton; Wong, Michael; Pepin, Robert; Elliott, Beverley; Spray, John; Thompson, Lucy; Gordon, Suzanne; Newsom, Horton; Ollila, Ann; Williams, Joshua; Vasconcelos, Paulo; Bentz, Jennifer; Nealson, Kenneth; Popa, Radu; Kah, Linda C.; Moersch, Jeffrey; Tate, Christopher; Day, Mackenzie; Kocurek, Gary; Hallet, Bernard; Sletten, Ronald; Francis, Raymond; McCullough, Emily; Cloutis, Ed; ten Kate, Inge Loes; Kuzmin, Ruslan; Arvidson, Raymond; Fraeman, Abigail; Scholes, Daniel; Slavney, Susan; Stein, Thomas; Ward, Jennifer; Berger, Jeffrey; Moores, John E.

2015-01-01

The Sample Analysis at Mars (SAM) investigation on the Mars Science Laboratory (MSL) Curiosity rover has detected oxidized nitrogen-bearing compounds during pyrolysis of scooped aeolian sediments and drilled sedimentary deposits within Gale crater. Total N concentrations ranged from 20 to 250 nmol N per sample. After subtraction of known N sources in SAM, our results support the equivalent of 110–300 ppm of nitrate in the Rocknest (RN) aeolian samples, and 70–260 and 330–1,100 ppm nitrate in John Klein (JK) and Cumberland (CB) mudstone deposits, respectively. Discovery of indigenous martian nitrogen in Mars surface materials has important implications for habitability and, specifically, for the potential evolution of a nitrogen cycle at some point in martian history. The detection of nitrate in both wind-drifted fines (RN) and in mudstone (JK, CB) is likely a result of N2 fixation to nitrate generated by thermal shock from impact or volcanic plume lightning on ancient Mars. Fixed nitrogen could have facilitated the development of a primitive nitrogen cycle on the surface of ancient Mars, potentially providing a biochemically accessible source of nitrogen. PMID:25831544

Evidence for indigenous nitrogen in sedimentary and aeolian deposits from the Curiosity rover investigations at Gale crater, Mars.

PubMed

Stern, Jennifer C; Sutter, Brad; Freissinet, Caroline; Navarro-González, Rafael; McKay, Christopher P; Archer, P Douglas; Buch, Arnaud; Brunner, Anna E; Coll, Patrice; Eigenbrode, Jennifer L; Fairen, Alberto G; Franz, Heather B; Glavin, Daniel P; Kashyap, Srishti; McAdam, Amy C; Ming, Douglas W; Steele, Andrew; Szopa, Cyril; Wray, James J; Martín-Torres, F Javier; Zorzano, Maria-Paz; Conrad, Pamela G; Mahaffy, Paul R

2015-04-07

The Sample Analysis at Mars (SAM) investigation on the Mars Science Laboratory (MSL) Curiosity rover has detected oxidized nitrogen-bearing compounds during pyrolysis of scooped aeolian sediments and drilled sedimentary deposits within Gale crater. Total N concentrations ranged from 20 to 250 nmol N per sample. After subtraction of known N sources in SAM, our results support the equivalent of 110-300 ppm of nitrate in the Rocknest (RN) aeolian samples, and 70-260 and 330-1,100 ppm nitrate in John Klein (JK) and Cumberland (CB) mudstone deposits, respectively. Discovery of indigenous martian nitrogen in Mars surface materials has important implications for habitability and, specifically, for the potential evolution of a nitrogen cycle at some point in martian history. The detection of nitrate in both wind-drifted fines (RN) and in mudstone (JK, CB) is likely a result of N2 fixation to nitrate generated by thermal shock from impact or volcanic plume lightning on ancient Mars. Fixed nitrogen could have facilitated the development of a primitive nitrogen cycle on the surface of ancient Mars, potentially providing a biochemically accessible source of nitrogen.

Surface texture analysis of southern Tuli Basin sediments: Implications for Limpopo Valley geoarchaeological contexts

NASA Astrophysics Data System (ADS)

Le Baron, Joel C.; Grab, Stefan W.; Kuman, Kathleen

2011-03-01

The Hackthorne 1 site (southern Tuli Basin, South Africa) is situated on a sand-covered plateau adjacent to the Limpopo River Valley. Although the site is well known for its Stone Age archaeology, the past environmental contexts (particularly sedimentological/geomorphological) are not well known. We examine the Hackthorne sand grain surface textures, so as to provide some insight on the site specific and regional depositional history. Quartz sands at Hackthorne were collected from surface sands and from underlying weathered calcrete. SEM analysis was performed on sand grains, through which several mechanical and chemical microtextures were identified. Microtextures typical of fluvial environments were found only on grains derived from the plateau calcrete host sediment, whilst the surface sands exhibited only textures associated with aeolian environments. The results indicate that the calcrete host sediment is composed of alluvium, and that the surface sands mantling the Hackthorne Plateau are not deflated from the alluvial deposits in the Limpopo Valley, but may rather be derived from distant aeolian sources. The deposition of aeolian sands is consistent with OSL dates which place sand deposition, or remobilization, at 23 and 15 kya, periods in southern Africa associated with increased aridity.

The provenance of Taklamakan desert sand

NASA Astrophysics Data System (ADS)

Rittner, Martin; Vermeesch, Pieter; Carter, Andrew; Bird, Anna; Stevens, Thomas; Garzanti, Eduardo; Andò, Sergio; Vezzoli, Giovanni; Dutt, Ripul; Xu, Zhiwei; Lu, Huayu

2016-03-01

Sand migration in the vast Taklamakan desert within the Tarim Basin (Xinjiang Uyghur Autonomous region, PR China) is governed by two competing transport agents: wind and water, which work in diametrically opposed directions. Net aeolian transport is from northeast to south, while fluvial transport occurs from the south to the north and then west to east at the northern rim, due to a gradual northward slope of the underlying topography. We here present the first comprehensive provenance study of Taklamakan desert sand with the aim to characterise the interplay of these two transport mechanisms and their roles in the formation of the sand sea, and to consider the potential of the Tarim Basin as a contributing source to the Chinese Loess Plateau (CLP). Our dataset comprises 39 aeolian and fluvial samples, which were characterised by detrital-zircon U-Pb geochronology, heavy-mineral, and bulk-petrography analyses. Although the inter-sample differences of all three datasets are subtle, a multivariate statistical analysis using multidimensional scaling (MDS) clearly shows that Tarim desert sand is most similar in composition to rivers draining the Kunlun Shan (south) and the Pamirs (west), and is distinctly different from sediment sources in the Tian Shan (north). A small set of samples from the Junggar Basin (north of the Tian Shan) yields different detrital compositions and age spectra than anywhere in the Tarim Basin, indicating that aeolian sediment exchange between the two basins is minimal. Although river transport dominates delivery of sand into the Tarim Basin, wind remobilises and reworks the sediment in the central sand sea. Characteristic signatures of main rivers can be traced from entrance into the basin to the terminus of the Tarim River, and those crossing the desert from the south to north can seasonally bypass sediment through the sand sea. Smaller ephemeral rivers from the Kunlun Shan end in the desert and discharge their sediment there. Both river run

The influence of groundwater depth on coastal dune development at sand flats close to inlets

NASA Astrophysics Data System (ADS)

Silva, Filipe Galiforni; Wijnberg, Kathelijne M.; de Groot, Alma V.; Hulscher, Suzanne J. M. H.

2018-05-01

A cellular automata model is used to analyze the effects of groundwater levels and sediment supply on aeolian dune development occurring on sand flats close to inlets. The model considers, in a schematized and probabilistic way, aeolian transport processes, groundwater influence, vegetation development, and combined effects of waves and tides that can both erode and accrete the sand flat. Next to three idealized cases, a sand flat adjoining the barrier island of Texel, the Netherlands, was chosen as a case study. Elevation data from 18 annual LIDAR surveys was used to characterize sand flat and dune development. Additionally, a field survey was carried out to map the spatial variation in capillary fringe depth across the sand flat. Results show that for high groundwater situations, sediment supply became limited inducing formation of Coppice-like dunes, even though aeolian losses were regularly replenished by marine import during sand flat flooding. Long dune rows developed for high sediment supply scenarios which occurred for deep groundwater levels. Furthermore, a threshold depth appears to exist at which the groundwater level starts to affect dune development on the inlet sand flat. The threshold can vary spatially depending on external conditions such as topography. On sand flats close to inlets, groundwater is capable of introducing spatial variability in dune growth, which is consistent with dune development patterns found on the Texel sand flat.

Fluvial sedimentary styles and associated depositional environments in the buntsandstein west of river rhine in saar area and pfalz (F.R. Germany) and vosges (France)

NASA Astrophysics Data System (ADS)

Dachroth, Wolfgang

The Buntsandstein west of river Rhine in Saar area, Pfalz and Vosges consists of three fluvial magnacycles which are characterized by different associated non-alluvial environments. The stratigraphic sequence is divided by several unconformities reflecting tectonic movements which were connected with periods of extension of the depositional area. Two major phases and two minor events are recognized by the evaluation of the Pfalz unconformity and the Lothringen unconformity, and the Leuter unconformity and the Saar unconformity, respectively. The Lower Buntsandstein (including Zechstein) compries the first magnacycle and is built up of alluvial-fan deposits, fluvial braidplain sediments and marine to lagoonal deposits. Some aeolian sands as well as several palaeosols are also present. The palaeolandscape consists of alluvial fans seaming the margin of the basin and fluvial braidplains reaching from the toes of the fan belt to the centre of the depositional area which is occupied by a lagoonal sea that partially evolves into a playa-lake with progressive refreshment. The Middle Buntsandstein comprises the second magnacycle and is composed of an alternation of aeolian Dünnschichten and fluvial Felsbänke. The third facies are alluvial-fan deposits of palaeogeographically restricted distribution along the margins of the basin. The aeolian Dünnschichten originate in the marginal parts of chott-type depressions (in comparison with the recent Chott Djerid in Tunesia) where rising ground water moistens the dry sediments that are laid down on the playa floor and thus allows their enhanced preservation. In dry periods, wind-blown sand is spread out as plane sheets or as migrating wind ripple trains, or accumulates to barchanoid-type dunes that advance across the flat. Depending on supply of sand, all stages of transition between dune fields with only narrow interdune corridors between the ridges and interdune playas with isolated widely-spaced dunes are developed. The

Impact of Aeolian Dry Deposition of Reactive Iron Minerals on Sulfur Cycling in Sediments of the Gulf of Aqaba

PubMed Central

Blonder, Barak; Boyko, Valeria; Turchyn, Alexandra V.; Antler, Gilad; Sinichkin, Uriel; Knossow, Nadav; Klein, Rotem; Kamyshny, Alexey

2017-01-01

The Gulf of Aqaba is an oligotrophic marine system with oxygen-rich water column and organic carbon-poor sediments (≤0.6% at sites that are not influenced by anthropogenic impact). Aeolian dust deposition from the Arabian, Sinai, and Sahara Deserts is an important source of sediment, especially at the deep-water sites of the Gulf, which are less affected by sediment transport from the Arava Desert during seasonal flash floods. Microbial sulfate reduction in sediments is inferred from the presence of pyrite (although at relatively low concentrations), the presence of sulfide oxidation intermediates, and by the sulfur isotopic composition of sulfate and solid-phase sulfides. Saharan dust is characterized by high amounts of iron minerals such as hematite and goethite. We demonstrated, that the resulting high sedimentary content of reactive iron(III) (hydr)oxides, originating from this aeolian dry deposition of desert dust, leads to fast re-oxidation of hydrogen sulfide produced during microbial sulfate reduction and limits preservation of reduced sulfur in the form of pyrite. We conclude that at these sites the sedimentary sulfur cycle may be defined as cryptic. PMID:28676799

Investigation into the Origin and Character of Surficial Sedimentary Deposits at the Midshore Regional Solid Waste Facility near Easton, Maryland

USGS Publications Warehouse

Smoot, Joseph P.; Newell, Wayne L.; DeJong, Benjamin D.

2009-01-01

A temporary exposure at the Midshore Regional Solid Waste Facility near Easton, MD, provided an opportunity to document the characteristics of the complex assemblage of surficial facies in that area. This unusually large cross section allowed interpretation of the changing processes that shaped the landscape in response to climate change through the late Pleistocene. Eight stratigraphic units were recognized: (1) gray, fossiliferous, muddy silt of the marine Miocene Choptank Formation; (2) coarse, crossbedded conglomerate of the late Miocene to Pliocene fluvial Pensauken Formation; (3) bioturbated muddy conglomerate interpreted as deposits of small colluvial fans; (4) pebbly, quartzose sand overlying a planar erosional surface reflecting a marine transgression; (5) irregular pods and lenses of sand and gravel deformed into bowl-shaped folds and faulted, which are interpreted as wind deposits over a semipermanent snow cover (niveo-aeolian deposits); (6) crossbedded sand and conglomerate with abundant mud partings indicating tidal influences on sinuous stream channels; (7) heavily bioturbated silt and sand with abundant root casts and flattened vesicles interpreted as aeolian loess deposits in marshy fens; and (8) pebbly sand and mud with scattered boulders and cobbles that reflect modern infill of the excavation by the operators. Soils formed on units 3, 4, and 7. Superimposed on units 4, 5, and 7 is evidence of deep freezing and permafrost development and subsequent thermokarst development after thawing, which includes large, complexly filled wedge-shaped cracks, deformed bedding and faults, fluid-injection structures, and spherical blobs of sand and mud. Each of the stratigraphic units has irregular distributions and lateral changes. The results of this study provide a unique insight into the geometry of surficial deposits that will help facilitate mapping of units, interpretation of cored intervals, and understanding of ground-penetrating radar profiles. The

Laboratory Simulations of Martian and Venusian Aeolian Processes

NASA Technical Reports Server (NTRS)

Greeley, Ronald

1999-01-01

With the flyby of the Neptune system by Voyager, the preliminary exploration of the Solar System was accomplished. Data have been returned for all major planets and satellites except the Pluto system. Results show that the surfaces of terrestrial planets and satellites have been subjected to a wide variety of geological processes. On solid- surface planetary objects having an atmosphere, aeolian processes are important in modifying their surfaces through the redistribution of fine-grained material by the wind. Bedrock may be eroded to produce particles and the particles transported by wind for deposition in other areas. This process operates on Earth today and is evident throughout the geological record. Aeolian processes also occur on Mars, Venus, and possibly Titan and Triton, both of which are outer planet satellites that have atmospheres. Mariner 9 and Viking results show abundant wind-related landforms on Mars, including dune fields and yardangs (wind-eroded hills). On Venus, measurements made by the Soviet Venera and Vega spacecraft and extrapolations from the Pioneer Venus atmospheric probes show that surface winds are capable of transporting particulate materials and suggest that aeolian processes may operate on that planet as well. Magellan radar images of Venus show abundant wind streaks in some areas, as well as dune fields and a zone of possible yardangs. The study of planetary aeolian processes must take into account diverse environments, from the cold, low-density atmosphere of Mars to the extremely hot, high- density Venusian atmosphere. Factors such as threshold wind speeds (minimum wind velocity needed to move particles), rates of erosion and deposition, trajectories of windblown particles, and aeolian flow fields over various landforms are all important aspects of the problem. In addition, study of aeolian terrains on Earth using data analogous to planetary data-collection systems is critical to the interpretation of spacecraft information and

Lunar and Planetary Science XXXV: Martian Aeolian and Mass Wasting Processes: Blowing and Flowing

NASA Technical Reports Server (NTRS)

2004-01-01

The session Martian Aeolian and Mass Wasting Processes: BLowing and Flowing included the following topics: 1) Three Decades of Martian Surface Changes; 2) Thermophysical Properties of Isidis Basin, Mars; 3) Intracrater Material in Eastern Arabia Terra: THEMIS, MOC, and MOLA Analysis of Wind-blown Deposits and Possible High-Inertia Source Material; 4) Thermal Properties of Sand from TES and THEMIS: Do Martian Dunes Make a Good Control for Thermal Inertia Calculations? 5) A Comparative Analysis of Barchan Dunes in the Intra-Crater Dune Fields and the North Polar Sand Sea; 6) Diluvial Dunes in Athabasca Valles, Mars: Morphology, Modeling and Implications; 7) Surface Profiling of Natural Dust Devils; 8) Martian Dust Devil Tracks: Inferred Directions of Movement; 9) Numerical Simulations of Anastomosing Slope Streaks on Mars; 10) Young Fans in an Equatorial Crater in Xanthe Terra, Mars; 11) Large Well-exposed Alluvual Fans in Deep Late-Noachian Craters; 12) New Evidence for the Formation of Large Landslides on Mars; and 13) What Can We Learn from the Ages of Valles Marineris Landslides on Martian Impact History?

Character and provenance of aeolian sediments in northeast Thailand

NASA Astrophysics Data System (ADS)

Nichol, Janet E.; Nichol, Douglas W.

2015-12-01

Aeolian activity is not generally associated with the humid tropics, and although reports of loess-like soils in various locations in southeast Asia exist, these mainly lack the detailed analysis to set them in meaningful spatial or historical context. This paper examines the red and yellow sandy sediments of the Khorat Plateau in northeast Thailand which have been variously referred to as 'cover sands', 'loessial soils' or 'loess'. The sediments are referred to as having alluvial, biological as well as aeolian origin, and a date of 9-35 ka is reported. The study compares the Khorat sediments physically and geochemically with loess and aeolian sediments from other regions, as well as with other sites in southeast Asia which are reported here. The moderate degree of particle sorting and unimodal sizes of the sediments along with a sub-spherical sub-rounded form, supports previous diagnoses of an aeolian origin. Geochemical analysis of the Khorat sediments indicates severe depletion in both mobile and immobile elements, which are even more depleted than other southeast Asian loessic soils examined. This depletion, along with the only moderate particle sorting, suggests the source of the sediments to be the local weathered sandstones outcropping around the edge of the Khorat Plateau. The dissimilarity of the Khorat sediments from Upper Continental Crust (UCC) elemental values supports this, as homogenisation would occur if diverse source areas were involved. The study suggests that aeolian sediments of humid tropical regions warrant more attention as climate proxy markers, due to the dissimilarity between the present climate and conditions required for their formation.

Boundary Conditions for Aeolian Activity in North American Dune Fields

NASA Astrophysics Data System (ADS)

Halfen, A. F.; Lancaster, N.; Wolfe, S.

2014-12-01

Geomorphic and chronological data for dune fields are evaluated for three contrasting areas of North America: 1) the Prairie-Parkland-Boreal ecozones of the northern Great Plains in Canada; 2) the Central Great Plains of the USA; and 3) the deserts of southwestern USA and northern Mexico. Luminescence and radiocarbon ages for periods of dune accumulation and stability are compared with palaeoenvironment proxies to provide an assessment of the boundary conditions of dune system response to changes in sediment supply, availability, and mobility. Dune fields in the northern Great Plains were formed from sediment originating from glaciofluvial or glaciolacustrine sediments deposited during deglaciation 16-11 ka. Subsequent aeolian deposition occurred in Parkland and Prairie dune fields as a result of mid-Holocene (8-5 ka) and late-Holocene (< 3.5 ka) activity related to drought conditions that reworked pre-existing aeolian sands. In the Central Great Plains, dune fields are closely linked to fluvial sediment sources. Sediment supply was high during deglaciation of the Rocky Mountains and resulted in widespread dune construction 16-10 ka. Multiple periods of Holocene reactivation are recorded and reflect increased sediment availability during drought episodes. Dune fields in the southwestern deserts experienced periods of construction as a result of enhanced supply of sediment from fluvial and lacustrine sources during the period 11.8-8 ka and at multiple intervals during the late Holocene. Despite spatial and temporal gaps in chronometric data as a result of sampling biases, the record from North American dune fields indicates the strong influence of sediment supply on dune construction, with changes in sediment availability as a result of drought episodes resulting in dune field reactivation and reworking of pre-existing sediment.

The effects of sorting by aeolian processes on the geochemical characteristics of surface materials: a wind tunnel experiment

NASA Astrophysics Data System (ADS)

Wang, Xunming; Lang, Lili; Hua, Ting; Zhang, Caixia; Li, Hui

2018-03-01

The geochemical characteristics of aeolian and surface materials in potential source areas of dust are frequently employed in environmental reconstructions as proxies of past climate and as source tracers of aeolian sediments deposited in downwind areas. However, variations in the geochemical characteristics of these aeolian deposits that result from near-surface winds are currently poorly understood. In this study, we collected surface samples from the Ala Shan Plateau (a major potential dust source area in Central Asia) to determine the influence of aeolian processes on the geochemical characteristics of aeolian transported materials. Correlation analyses show that compared with surface materials, the elements in transported materials (e.g., Cu, As, Pb, Mn, Zn, Al, Ca, Fe, Ga, K, Mg, P, Rb, Co, Cr, Na, Nb, Si, and Zr) were subjected to significant sorting by aeolian processes, and the sorting also varied among different particle size fractions and elements. Variations in wind velocity were significantly correlated with the contents of Cr, Ga, Sr, Ca, Y, Nd, Zr, Nb, Ba, and Al, and with the Zr/Al, Zr/Rb, K/Ca, Sr/Ca, Rb/Sr, and Ca/Al ratios. Given the great variation in the geochemical characteristics of materials transported under different aeolian processes relative to those of the source materials, these results indicate that considerable uncertainty may be introduced to analyses by using surface materials to trace the potential source areas of aeolian deposits that accumulate in downwind areas.

Hydraulic experiment on tsunami sand deposits relating with grain size distribution and magnitude of incident waves

NASA Astrophysics Data System (ADS)

Yamamoto, A.; Takahashi, T.; Harada, K.; Nojima, K.

2016-12-01

A huge earthquake occurred off the Tohoku district in Japan on March 11th, 2011. A massive tsunami generated by the earthquake attacked coastal areas and caused serious damage. The tsunami disaster requires to reconsider tsunami measures in the Nankai Trough. Many of the measures are based on histories of large earthquakes and tsunamis. Because they are low frequency disasters and their historical documents are limited, tsunami sand deposits have been expected to analyze paleotsunamis. Tsunami sand deposits, however, are only used to confirm the fact of tsunamis and to determine the relative magnitudes. The thickness of sand layer and the grain size may be clues to estimate the tsunami force. Further, it could reveal the tsunami source. These results are also useful to improve the present tsunami measures. The objective of this study is to investigate the formation mechanism of tsunami sand deposits by hydraulic experiment. A two-dimensional water channel consisted of a wave maker, a flat section and a slope section. A movable bed section with various grain sizes and distribution of sand was set at the end of flat section. Bore waves of several heights transported the sand to the slope section by run-up. Water surface elevation and velocity were measured at several points. Tsunami sand deposit distribution was also measured along the slope section. The experimental result showed that the amount of tsunami sand deposit was relating with the grain size distribution and the magnitude of incident waves. Further, the number of incident waves affected the profile of tsunami sand deposits.

Modeling Cape- and Ridge-Associated Marine Sand Deposits; A Focus on the U.S. Atlantic Continental Shelf

USGS Publications Warehouse

Bliss, James D.; Williams, S. Jeffress; Bolm, Karen S.

2009-01-01

Cape- and ridge-associated marine sand deposits, which accumulate on storm-dominated continental shelves that are undergoing Holocene marine transgression, are particularly notable in a segment of the U.S. Atlantic Continental Shelf that extends southward from the east tip of Long Island, N.Y., and eastward from Cape May at the south end of the New Jersey shoreline. These sand deposits commonly contain sand suitable for shore protection in the form of beach nourishment. Increasing demand for marine sand raises questions about both short- and long-term potential supply and the sustainability of beach nourishment with the prospects of accelerating sea-level rise and increasing storm activity. To address these important issues, quantitative assessments of the volume of marine sand resources are needed. Currently, the U.S. Geological Survey is undertaking these assessments through its national Marine Aggregates and Resources Program (URL http://woodshole.er.usgs.gov/project-pages/aggregates/). In this chapter, we present a hypothetical example of a quantitative assessment of cape-and ridge-associated marine sand deposits in the study area, using proven tools of mineral-resource assessment. Applying these tools requires new models that summarize essential data on the quantity and quality of these deposits. Two representative types of model are descriptive models, which consist of a narrative that allows for a consistent recognition of cape-and ridge-associated marine sand deposits, and quantitative models, which consist of empirical statistical distributions that describe significant deposit characteristics, such as volume and grain-size distribution. Variables of the marine sand deposits considered for quantitative modeling in this study include area, thickness, mean grain size, grain sorting, volume, proportion of sand-dominated facies, and spatial density, of which spatial density is particularly helpful in estimating the number of undiscovered deposits within an

A Fuzzy Cognitive Model of aeolian instability across the South Texas Sandsheet

NASA Astrophysics Data System (ADS)

Houser, C.; Bishop, M. P.; Barrineau, C. P.

2014-12-01

Characterization of aeolian systems is complicated by rapidly changing surface-process regimes, spatio-temporal scale dependencies, and subjective interpretation of imagery and spatial data. This paper describes the development and application of analytical reasoning to quantify instability of an aeolian environment using scale-dependent information coupled with conceptual knowledge of process and feedback mechanisms. Specifically, a simple Fuzzy Cognitive Model (FCM) for aeolian landscape instability was developed that represents conceptual knowledge of key biophysical processes and feedbacks. Model inputs include satellite-derived surface biophysical and geomorphometric parameters. FCMs are a knowledge-based Artificial Intelligence (AI) technique that merges fuzzy logic and neural computing in which knowledge or concepts are structured as a web of relationships that is similar to both human reasoning and the human decision-making process. Given simple process-form relationships, the analytical reasoning model is able to map the influence of land management practices and the geomorphology of the inherited surface on aeolian instability within the South Texas Sandsheet. Results suggest that FCMs can be used to formalize process-form relationships and information integration analogous to human cognition with future iterations accounting for the spatial interactions and temporal lags across the sand sheets.

Aeolian saltation on Mars at low wind speeds

NASA Astrophysics Data System (ADS)

Sullivan, R.; Kok, J. F.

2017-10-01

Laboratory experiments indicate that the fluid threshold friction speed, u*tf, required to initiate fully developed aeolian saltation is much higher on Mars than on Earth. A discrepancy exists between Mars climate models that do not predict winds this strong and observations that sand-sized particles are indeed moving. This paper describes how wind friction speeds well below u*tf, but above the impact threshold, u*ti, required to sustain saltation, can initiate sustained saltation on Mars, but at relatively low flux. Numerical experiments indicate that a sand grain on Mars mobilized sporadically between u*ti and u*tf will develop, over fetch lengths longer than generally available within low-pressure wind tunnels, trajectories capable of splashing grains that propagate saltation and collectively form a cluster of saltating grains that migrate downwind together. The passage of a saltation cluster should leave behind a narrow zone of affected surface grains. The cumulative effect of many clusters represents a low-flux phenomenon that should produce slow changes to aeolian bedforms over periods in which winds remain close to u*ti and never or rarely reach u*tf. Field evidence from small impact ripples along rover traverses is consistent with effects of saltation at these low friction speeds, without obvious evidence for events ≥u*tf. The potential utility of this grain mobility process is that it can operate entirely at more common winds well below u*tf and so help explain widespread sand movements observed on Mars wherever evidence might be mostly absent for u*tf being exceeded.

The physics of wind-blown sand and dust

NASA Astrophysics Data System (ADS)

Kok, Jasper F.; Parteli, Eric J. R.; Michaels, Timothy I.; Karam, Diana Bou

2012-10-01

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

The physics of wind-blown sand and dust.

PubMed

Kok, Jasper F; Parteli, Eric J R; Michaels, Timothy I; Karam, Diana Bou

2012-10-01

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

Facies architecture and high resolution sequence stratigraphy of an aeolian, fluvial and shallow marine system in the Pennsylvanian Piauí Formation, Parnaíba Basin, Brazil

NASA Astrophysics Data System (ADS)

Vieira, Lucas Valadares; Scherer, Claiton Marlon dos Santos

2017-07-01

The Pennsylvanian Piauí Formation records the deposition of aeolian, fluvial and shallow marine systems accumulated in the cratonic sag Parnaíba basin. Characterization of the facies associations and sequence stratigraphic framework was done by detailed description and logging of outcrops. Six facies associations were recognized: aeolian dunes and interdunes, aeolian sandsheets, fluvial channels, tidally-influenced fluvial channels, shoreface and shoreface-shelf transition. Through correlation of stratigraphic surfaces, the facies associations were organized in system tracts, which formed eight high frequency depositional sequences, bounded by subaerial unconformities. These sequences are composed of a lowstand system tract (LST), that is aeolian-dominated or fluvial-dominated, a transgressive system tract (TST) that is formed by tidally-influenced fluvial channels and/or shoreface and shoreface-shelf transition deposits with retrogradational stacking, and a highstand system tract (HST), which is formed by shoreface-shelf transition and shoreface deposits with progradational stacking. Two low frequency cycles were determined by observing the stacking of the high frequency cycles. The Lower Sequence is characterized by aeolian deposits of the LST and an aggradational base followed by a progressive transgression, defining a general TST. The Upper Sequence is characterized by fluvial deposits and interfluve pedogenesis concurring with the aeolian deposits of the LST and records a subtle regression followed by transgression. The main control on sedimentation in the Piauí Formation was glacioeustasy, which was responsible for the changes in relative sea level. Even though, climate changes were associated with glacioeustatic phases and influenced the aeolian and fluvial deposition.

A wind tunnel study of aeolian sediment transport response to unsteady winds

NASA Astrophysics Data System (ADS)

Li, Bailiang; McKenna Neuman, Cheryl

2014-06-01

Although moderate attention has been paid to the response of the aeolian mass transport rate to wind gusts, it is still unclear how the particle size and volumetric concentration affect this relation. Very little is known about the response time of the particle speed, and specifically, how the sensor scale and elevation affect measurements of this variable. The present study addresses this knowledge gap through a series of wind tunnel experiments in which a gusty wind was generated by programming the fan motor to adjust to a randomly selected rpm every 10 s. Beds consisting of either medium or coarse sand were investigated through synchronous, co-located measurements of the local wind speed and particle speed/count rate obtained via a customized laser Doppler anemometry (LDA) system. The vertically integrated sand transport rate (Q) and the wind speed in the freestream were quantified using a passive sand trap and pitot tube, respectively. The results of the experiments indicate that the response of the aeolian transport system to wind gusts is generally faster in terms of the particle speed than the mass transport rate, while the degree of correlation is found to vary with the sensor elevation, as well as with the particle size and volumetric concentration. In essence, the coupling within the transport system is demonstrated to be strongly scale dependent.

Aeolian dust in Colorado Plateau soils: Nutrient inputs and recent change in source

PubMed Central

Reynolds, Richard; Belnap, Jayne; Reheis, Marith; Lamothe, Paul; Luiszer, Fred

2001-01-01

Aeolian dust (windblown silt and clay) is an important component in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to dust-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian dust in arid regions and to evaluate the roles of this dust in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A component of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian dust component is typically as much as 20–30%. Dust inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective dust traps that apparently record a change in dust sources over the past several decades. Some of the recently fallen dust may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt. PMID:11390965

Aeolian dust in Colorado Plateau soils: Nutrient inputs and recent change in source

USGS Publications Warehouse

Reynolds, R.; Belnap, Jayne; Lamothe, Paul; Luiszer, Fred

2001-01-01

Aeolian dust (windblown silt and clay) is an important component in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to dust-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian dust in arid regions and to evaluate the roles of this dust in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A component of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian dust component is typically as much as 20a??30%. Dust inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective dust traps that apparently record a change in dust sources over the past several decades. Some of the recently fallen dust may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt.

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

Biodiversity impact of the aeolian periglacial geomorphologic evolution of the Fontainebleau Massif (France)

NASA Astrophysics Data System (ADS)

Thiry, M.; Liron, M. N.

2009-04-01

erosion of the sand beneath the bordering sandstone benches, resulting in overhangs. These structures are the most common in the western district of the Fontainebleau Massif. Ponds develop on the tightly silicified and impermeable sandstone pans that form the "platières". There are permanent ponds and temporary wet zones, formed of interconnected or isolated depressions. The origin of these ponds has to be questioned with regard to the landscape shaping. Their origin is directly bound to the hollowing of uncemented, sandy zones, within the sandstone pans forming the "platières". Erosion by runoff cannot be considered; the only way to hollow them out is by deflation processes. No direct dating of the Quaternary dune and loess deposits of the Fontainebleau Massif exists. Nevertheless, dating of paleopodzols interlayered between drift sands, pond deposits and bones within congelifracts allow relating these periglacial features with the end of the last glacial period. For now, there is no dating to assess what belongs to older glacial periods. Distribution of the aeolian patterns The Fontainebleau Massif displays noteworthy morphological diversities in the various districts of the forest. Some of these differentiations result from geological features, but most of them are related to erosion processes, and among them deflation processes leaved different imprints in the western and eastern districts of the Fontainebleau Massif. The topography played an important role controlling the aeolian processes. Deflation was important in the westerly upwind district. In the westerly front face, aeolian erosion was activated by turbulences around the topographic obstacles. The reliefs funneled the winds and gave rise to swirls that hollow the blowouts. This area displays the sharpest and more chiseled landforms of the massif. Moreover, the sandstone scarps at the edge of the "platières" are high and uncovered, with frequent overhangs. The collapsed sandstone blocks of the "chaos" are

Sand deposition in the Colorado River in the Grand Canyon from flooding of the Little Colorado River

USGS Publications Warehouse

Wiele, S.M.; Graf, J.B.; Smith, J.D.

1996-01-01

Methods for computing the volume of sand deposited in the Colorado River in Grand Canyon National Park by floods in major tributaries and for determining redistribution of that sand by main-channel flows are required for successful management of sand-dependent riparian resources. We have derived flow, sediment transport, and bed evolution models based on a gridded topography developed from measured channel topography and used these models to compute deposition in a short reach of the river just downstream from the Little Colorado River, the largest tributary in the park. Model computations of deposition from a Little Colorado River flood in January 1993 were compared to bed changes measured at 15 cross sections. The total difference between changes in cross-sectional area due to deposition computed by the model and the measured changes was 6%. A wide reach with large areas of recirculating flow and large depressions in the main channel accumulated the most sand, whereas a reach with similar planimetric area but a long, narrow shape and relatively small areas of recirculating flow and small depressions in the main channel accumulated only about a seventh as much sand. About 32% of the total deposition was in recirculation zones, 65% was in the main channel, and 3% was deposited along the channel margin away from the recirculation zone. Overall, about 15% of the total input of sand from this Little Colorado River flood was deposited in the first 3 km below the confluence, suggesting that deposition of the flood-derived material extended for only several tens of kilometers downstream from the confluence.

Seasonally Active Slipface Avalanches in the North Polar Sand Sea of Mars: Evidence for a Wind-Related Origin

NASA Technical Reports Server (NTRS)

Horgan, Briony H. N.; Bell, James F., III

2012-01-01

Meter-scale MRO/HiRISE camera images of dune slipfaces in the north polar sand sea of Mars reveal the presence of deep alcoves above depositional fans. These features are apparently active under current climatic conditions, because they form between observations taken in subsequent Mars years. Recently, other workers have hypothesized that the alcoves form due to destabilization and mass-wasting during sublimation of CO2 frost in the spring. While there is evidence for springtime modification of these features, our analysis of early springtime images reveals that over 80% of the new alcoves are visible underneath the CO2 frost. Thus, we present an alternative hypothesis that formation of new alcoves and fans occurs prior to CO2 deposition. We propose that fans and alcoves form primarily by aeolian processes in the mid- to late summer, through a sequence of aeolian deposition on the slipface, over-steepening, failure, and dry granular flow. An aeolian origin is supported by the orientations of the alcoves, which are consistent with recent wind directions. Furthermore, morphologically similar but much smaller alcoves form on terrestrial dune slipfaces, and the size differences between the terrestrial and Martian features may reflect cohesion in the near-subsurface of the Martian features. The size and preservation of the largest alcoves on the Martian slipfaces also support the presence of an indurated surface layer; thus, new alcoves might be sites of early spring CO2 sublimation and secondary mass-wasting because they act as a window to looser, less indurated materials that warm up more quickly in the spring.

Divergent taxonomic and functional responses of microbial communities to field simulation of aeolian soil erosion and deposition.

PubMed

Ma, Xingyu; Zhao, Cancan; Gao, Ying; Liu, Bin; Wang, Tengxu; Yuan, Tong; Hale, Lauren; Nostrand, Joy D Van; Wan, Shiqiang; Zhou, Jizhong; Yang, Yunfeng

2017-08-01

Aeolian soil erosion and deposition have worldwide impacts on agriculture, air quality and public health. However, ecosystem responses to soil erosion and deposition remain largely unclear in regard to microorganisms, which are the crucial drivers of biogeochemical cycles. Using integrated metagenomics technologies, we analysed microbial communities subjected to simulated soil erosion and deposition in a semiarid grassland of Inner Mongolia, China. As expected, soil total organic carbon and plant coverage were decreased by soil erosion, and soil dissolved organic carbon (DOC) was increased by soil deposition, demonstrating that field simulation was reliable. Soil microbial communities were altered (p < .039) by both soil erosion and deposition, with dramatic increase in Cyanobacteria related to increased stability in soil aggregates. amyA genes encoding α-amylases were specifically increased (p = .01) by soil deposition and positively correlated (p = .02) to DOC, which likely explained changes in DOC. Surprisingly, most of microbial functional genes associated with carbon, nitrogen, phosphorus and potassium cycling were decreased or unaltered by both erosion and deposition, probably arising from acceleration of organic matter mineralization. These divergent responses support the necessity to include microbial components in evaluating ecological consequences. Furthermore, Mantel tests showed strong, significant correlations between soil nutrients and functional structure but not taxonomic structure, demonstrating close relevance of microbial function traits to nutrient cycling. © 2017 John Wiley & Sons Ltd.

Modeling of flood-deposited sand distributions in a reach of the Colorado River below the Little Colorado River, Grand Canyon, Arizona

USGS Publications Warehouse

Wiele, S.M.

1998-01-01

A release from Glen Canyon Dam during March-April 1996 was designed to test the effectiveness with which the riparian environment could be renewed with discharges greatly in excess of the normal powerplant-restricted maximum. Of primary concern was the rebuilding of sand deposits along the channel sides that are important to the flora and fauna along the river corridor and that provide the only camp sites for riverside visitors to the Grand Canyon National Park. Analysis of the depositional processes with a model of flow, sand transport, and bed evolution shows that the sand deposits formed along the channel sides early during the high flow were affected only slightly by the decline in suspended-sand concentrations over the course of the controlled flood. Modeling results suggest that the removal of a large sand deposit over several hours was not a response to declining suspended-sand concentrations. Comparisons of the controlled-flood deposits with deposits formed during a flood in January 1993 on the Little Colorado River that contributed sufficient sand to raise the suspended-sand concentrations to predam levels in the main stem show that the depositional pattern as well as the magnitude is strongly influenced by the suspended-sand concentrations.

Wind-invariant saltation heights imply linear scaling of aeolian saltation flux with shear stress.

PubMed

Martin, Raleigh L; Kok, Jasper F

2017-06-01

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation-the wind-driven transport of sand in hopping trajectories-scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies. These results support the assumption of constant particle speeds in recent models predicting linear scaling of saltation flux with shear stress. In contrast, our results refute widely used older models that assume that particle speed increases with shear velocity, thereby predicting nonlinear 3/2 stress-flux scaling. This conclusion is further supported by direct field measurements of saltation flux versus shear stress. Our results thus argue for adoption of linear saltation flux laws and constant saltation trajectories for modeling saltation-driven aeolian processes on Earth, Mars, and other planetary surfaces.

Wind-invariant saltation heights imply linear scaling of aeolian saltation flux with shear stress

PubMed Central

Martin, Raleigh L.; Kok, Jasper F.

2017-01-01

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the flux of particles in aeolian saltation—the wind-driven transport of sand in hopping trajectories—scales with wind speed, largely because models do not agree on how particle speeds and trajectories change with wind shear velocity. We present comprehensive measurements, from three new field sites and three published studies, showing that characteristic saltation layer heights remain approximately constant with shear velocity, in agreement with recent wind tunnel studies. These results support the assumption of constant particle speeds in recent models predicting linear scaling of saltation flux with shear stress. In contrast, our results refute widely used older models that assume that particle speed increases with shear velocity, thereby predicting nonlinear 3/2 stress-flux scaling. This conclusion is further supported by direct field measurements of saltation flux versus shear stress. Our results thus argue for adoption of linear saltation flux laws and constant saltation trajectories for modeling saltation-driven aeolian processes on Earth, Mars, and other planetary surfaces. PMID:28630907

The chemistry of Saudi Arabian sand: A deposition problem on helicopter turbine airfoils

NASA Technical Reports Server (NTRS)

Smialek, James L.

1991-01-01

Recent operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz (Ca,Mg) CO3 dolomite, CaCO3 calcite, and occasionally CaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 0.25 in. thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of GaSO4.

The chemistry of Saudi Arabian sand - A deposition problem on helicopter turbine airfoils

NASA Astrophysics Data System (ADS)

Smialek, James L.; Archer, Frances A.; Garlick, Ralph G.

Operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz, (Ca,Mg)CO3 dolomite, CaCO3 calcite, and occasionally NaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 5 mm thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of CaSO4.

The Chemistry of Saudi Arabian Sand - A Deposition Problem on Helicopter Turbine Airfoils

NASA Technical Reports Server (NTRS)

Smialek, James L.; Archer, Frances A.; Garlick, Ralph G.

1992-01-01

Operations in the Persian Gulf have exposed military helicopter turbines to excessive amounts of ingested sand. Fine particles, less than 10 microns, are able to bypass the particle separators and enter the cooling and combustion systems. The initial sand chemistry varies by location, but is made up of a calcium aluminum silicate glass, SiO2 low quartz, (Ca,Mg)CO3 dolomite, CaCO3 calcite, and occasionally NaCl rocksalt. The sand reacts in the hot combustion gases and deposits onto the turbine vanes as CaSO4, glass, and various crystalline silicates. Deposits up to 5 mm thick have been collected. Although cooling hole plugging is a considerable problem, excessive corrosion is not commonly observed due to the high melting point of CaSO4.

The developmental trend and influencing factors of aeolian desertification in the Zoige Basin, eastern Qinghai-Tibet Plateau

NASA Astrophysics Data System (ADS)

Hu, Guangyin; Dong, Zhibao; Lu, Junfeng; Yan, Changzhen

2015-12-01

The Zoige Basin is located in the northeastern region of the Qinghai-Tibet Plateau and covers an area of 19,400 km2. At a mean altitude of 3500 m, the basin is highly sensitive to global environmental change and human disturbance due to its high elevation and fragile cold environment. The process of aeolian desertification in the basin can be clearly recognized in Landsat images that show the development of sand sheets and dunes over time. To monitor the spatial and temporal changes of aeolian desertification in the Zoige Basin, we analyzed Landsat images recorded in 1975, 1990, 2000, 2005, and 2010. Results showed that aeolian desertification increased rapidly from 1975 to 1990, was stable from 1990 to 2000, decreased slightly from 2000 to 2005, and decreased sharply from 2005 to 2010. Increasing temperature, overgrazing, rodent damage, and drainage of wetlands were considered the key driving factors of the expansion of aeolian desertification. A number of political measures were initiated in the 1990s to slow desertification, but the countermeasures of grazing prohibition, enclosures, and paving straw checkerboard barriers were not implemented until around 2005. These measures resulted in a dramatic recovery of aeolian desertified land between 2005 and 2010. Based on the cause analysis, anthropogenic factors were identified as the dominant driving force for both development and recovery of aeolian desertified land.

Aeolian processes during the Holocene in Gannan Region, Eastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Yang, S.; Cheng, T.; Li, S.; Liang, M.

2016-12-01

Aeolian desertification occurring in the Tibetan Plateau has received attention recently for it has become a severe environmental problem by accelerating the grassland degradation and eco-environment damage. The Gannan Region is located in the northeastern Tibetan Plateau with a mean altitude of 3500m. It is highly sensitive to global environmental change and human disturbance. Serious soil erosion and desertification and extensive land degradation have caused heavy eco-environmental impacts. To investigate the evolution of the desertification in Holocene in the Plateau is of great importance for understanding the desertification trend under the global changes in the Tibetan Plateau. Loess and aeolian sands is a key geological archive related to desertification processes and the past environment changes. In this study a typical 8.5m-thick loess-sands profile named MQQ, was selected at the Maqu city. It is situated on the first terrace (T1) of the Yellow River. Detailed accelerator mass spectrometry (AMS) 14C dating of bulk organic matter content has shown the Aeolian sediments of the MQQ section occurring since the early Holocene. the mass-specific frequency-dependent magnetic susceptibility (χfd) and grainsize records show a clear upward increase in the contents of superparamagnetic grains and fine fractions in grain size, which indicates a gradual wetting trend during the Holocene.The sediment rates change from very high in the early Holocene to low values after 8.2 ka. The wetting process can be divided into three steps: 10.0-8.2 ka, 8.2-3.0 ka and 3.0-present. It indicates that the climate in the eastern Tibetan Plateau was dry during the early Holocene. After that the climate was getting wet gradually. The variations of the westerlies and the Asian monsoon may cause the environmental change in this region.

Topography and geologic characteristics of aeolian grooves in the south polar layered deposits of Mars

USGS Publications Warehouse

Bridges, N.T.; Herkenhoff, K. E.

2002-01-01

The topographic and geologic characteristics of grooves and groove-like features in the south polar layered deposits near the Mars Polar Lander/Deep Space 2 landing sites are evaluated using Mariner 9 images and their derived photoclinometry, normalized using Mars Orbiter Laser Altimeter data. Although both Mariner 9 and Viking images of the south polar layered deposits were available at the time of this study, Mariner 9 images of the grooves were selected because they were generally of higher resolution than Viking images. The dimensions and slopes of the grooves, together with orientations that nearly match the strongest winds predicted in the Martian Global Circulation Model and directions inferred from other wind indicators, suggest that they formed by aeolian scour of an easily erodible surface. Most grooves are symmetric and V-shaped in transverse profile, inconsistent with an origin involving extensional brittle deformation. Although the grooves strike along slopes and terraces of the south polar layered deposits, the variable depths and lack of terracing within the grooves themselves indicate that any stratigraphy in the uppermost 100 m of the polar layered deposits is composed of layers of similar, and relatively low, resistance. The grooves do not represent landing hazards at the scale of the Mariner 9 images (72-86 m/pixel) and therefore probably would not have affected Mars Polar Lander and Deep Space 2, had they successfully reached the surface. ?? 2002 Elsevier Science (USA).

Mineral Resource Assessment of Marine Sand Resources in Cape- and Ridge-Associated Marine Sand Deposits in Three Tracts, New York and New Jersey, United States Atlantic Continental Shelf

USGS Publications Warehouse

Bliss, James D.; Williams, S. Jeffress; Arsenault, Matthew A.

2009-01-01

Demand is growing in the United States and worldwide for information about the geology of offshore continental shelf regions, the character of the seafloor, and sediments comprising the seafloor and subbottom. Interest in locating sand bodies or high quality deposits that have potential as sources for beach nourishment and ecosystem restoration is especially great in some regions of the country. The Atlantic coast, particularly New York and New Jersey, has been the focus of these studies for the past 40 years with widely varying results. This study is the first attempt at applying probability statistics to modeling Holocene-age cape-and ridge-associated sand deposits and thus focuses on distinct sand body morphology. This modeling technique may have application for other continental shelf regions that have similar geologic character and late Quaternary sea-level transgression history. An estimated volume of 3.9 billion m3 of marine sand resources is predicted in the cape-and ridge-associated marine sand deposits in three representative regions or tracts on the continental shelf offshore of New York and New Jersey. These estimates are taken from probabilistic distributions of sand resources and are produced using deposit models and Monte Carlo Simulation (MCS) techniques. The estimated sand resources presented here are for only three tracts as described below and for Holocene age sand resources contained in cape-and ridge-associated marine sand deposit types within this area. Other areas may qualify as tracts for this deposit type and other deposit types and geologic ages (for example, paleo-stream channels, blanket and outwash deposits, ebb-tide shoals, and lower sea level-stand deltas), which are present on the New Jersey and New York continental shelf area but are not delineated and modeled in this initial evaluation. Admittedly, only a portion of these probable sand resources will ultimately be available and suitable for production, dependent largely on

Preliminary study of Kelso Dunes using AVIRIS, TM, and AIRSAR

NASA Technical Reports Server (NTRS)

Xu, Pung; Blumberg, Dan G.; Greeley, Ronald

1995-01-01

Remote sensing of sand dunes helps in the understanding of aeolian process and provides important information about the regional geologic history, environmental change, and desertification. Remotely sensed data combined with field studies are valuable in studying dune morphology, regional aeolian dynamics, and aeolian depositional history. In particular, active and inactive sands of the Kelso Dunes have been studied using landsat TM and AIRSAR. In this report, we describe the use of AVIRIS data to study the Kelso dunes and to compare the AVIRIS information with that from TM and AIRSAR.

Depositional analysis of Hill sand of Rodessa Formation (lower Cretaceous) in north Shongaloo-Red Rock field, Webster Parish, Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamick, J.A.; Sartin, A.A.

1988-09-01

Hill sand is an informal subdivision of the Lower Cretaceous Rodessa Formation and is a common hydrocarbon reservoir in northeastern Texas, northern Louisiana, and southern Arkansas. The Hill sand is lithologically variable within the study area and consists of conglomerate, fine-grained sandstone, siltstone, mottled red-green claystone, black shale, and limestone. Five depositional environments were interpreted for lithofacies present in Hill sand cores from the North Shongaloo-Red Rock field. These include facies A, fluvial point bar; facies B, crevasse system; facies C, interdistributary bay; facies D, swamp; and facies E, carbonate interdistributary bay. Fluvial point bar and crevasse deposits commonly formmore » hydrocarbon reservoirs in the field. On a regional scale, depositional environments observed in the Hill sand include several fluvial deposystems trending northeast-southwest through Webster Parish. These deposystems terminate into deltaic distributary mouth bars along a northwest-southeast-trending coastline. Areas west of the coastline were occupied by shallow marine environments. Interchannel areas east of the coastline were occupied by interdistributary bay, lake, and crevasse environments in lower deltaic areas, and by lake, swamp, and crevasse environments in upper deltaic areas. Lowermost deposits of the Hill sand throughout the region are interpreted to consist of shallow marine environments. These marine deposits were overlain by thick, predominantly nonmarine sediments. Near the end of Hill sand deposition, the entire region was covered by very shallow marine environments, prior to deposition of the overlying First Lower Anhydrite Stringer.« less

Gone But Not Forgotten: The Aeolian Modification of Fluvial Surfaces on Mars: Preliminary Results from Central Australia

NASA Technical Reports Server (NTRS)

Bourke, M. C.

2003-01-01

MOC images indicate that aeolian ridges may mask and even obliterate primary depositional surfaces on Mars. This modification increases the difficulty in mapping the recent geological history of the planet. An analogue study in central Australia demonstrates how patterns in aeolian dunes, formed over abandoned fluvial surfaces, can be used to detect buried fluvial features.

Growth pattern research on the modern deposition of Ganjiang delta in Poyang lake basin by spatio-temporal remote sensing images

NASA Astrophysics Data System (ADS)

Zhou, Hongying; Yuan, Xuanjun; Zhang, Youyan; Dong, Wentong; Liu, Song

2016-11-01

It is of great importance for petroleum exploration to study the sedimentary features and the growth pattern of shoal water deltas in lake basins. Taking spatio-temporal remote sensing images as the principal data source, combined with field sedimentation survey, a quantitative research on the modern deposition of Ganjiang delta in the Poyang Lake Basin is described in this paper. Using 76 multi-temporal and multi-type remote sensing images acquired from 1973 to 2015, combined with field sedimentation survey, remote sensing interpretation analysis was conducted on the sedimentary facies of the Ganjiang delta. It is found that that the current Poyang Lake mainly consists of three types of sand body deposits including deltaic deposit, overflow channel deposit, and aeolian deposit, and the distribution of sand bodies was affected by the above three types of depositions jointly. The mid-branch channels of the Ganjiang delta increased on an exponential growth rhythm. The main growth pattern of the Ganjiang delta is dendritic and reticular, and the distributary channel mostly arborizes at lake inlet and was reworked to be reticulatus at late stage.

The role of detrital anhydrite in diagenesis of aeolian sandstones (Upper Rotliegend, The Netherlands): Implications for reservoir-quality prediction

NASA Astrophysics Data System (ADS)

Henares, S.; Bloemsma, M. R.; Donselaar, M. E.; Mijnlieff, H. F.; Redjosentono, A. E.; Veldkamp, H. G.; Weltje, G. J.

2014-12-01

The Rotliegend (Upper Permian) reservoir interval in the Southern Permian Basin (SPB) contains low-permeability streaks corresponding to anhydrite-cemented intervals. An integrated study was conducted using core, cuttings, thin sections and well-log data from a gas exploration well and two geothermal wells that target the zone of interest. This study aims at understanding the origin and nature of these low-permeability streaks, as well as their impact on reservoir properties, and to establish a predictive model of their spatial distribution. High-resolution XRF core-scanning analysis allowed to extrapolate spot observations in thin sections to the entire core. Diagenetic history includes grain rearrangement and anhydrite, haematitic clay coatings, dolomite rims, quartz overgrowths, kaolinite and second-generation carbonates as cementing phases. Coupling of all data reveals the detrital origin of the anhydrite/gypsum grains which were deposited together with the coarse-grained sand fraction in an aeolian sandflat environment. Such partially or completely dissolved grains acted as local sources of anhydrite cement and as nuclei for precipitation, explaining its preferential occurrence in coarse-grained laminae. Thick gypscretes in the vicinity likely supplied the anhydrite/gypsum grains. A conceptual model is proposed, including the location of nearby gypscretes and the prevailing west-southwest aeolian transport direction on the southern rim of the SPB.

Oil sands development and its impact on atmospheric wet deposition of air pollutants to the Athabasca Oil Sands Region, Alberta, Canada.

PubMed

Lynam, Mary M; Dvonch, J Timothy; Barres, James A; Morishita, Masako; Legge, Allan; Percy, Kevin

2015-11-01

Characterization of air pollutant deposition resulting from Athabasca oil sands development is necessary to assess risk to humans and the environment. To investigate this we collected event-based wet deposition during a pilot study in 2010-2012 at the AMS 6 site 30 km from the nearest upgrading facility in Fort McMurray, AB, Canada. Sulfate, nitrate and ammonium deposition was (kg/ha) 1.96, 1.60 and 1.03, respectively. Trace element pollutant deposition ranged from 2 × 10(-5) - 0.79 and exhibited the trend Hg < Se < As < Cd < Pb < Cu < Zn < S. Crustal element deposition ranged from 1.4 × 10(-4) - 0.46 and had the trend: La < Ce < Sr < Mn < Al < Fe < Mg. S, Se and Hg demonstrated highest median enrichment factors (130-2020) suggesting emissions from oil sands development, urban activities and forest fires were deposited. High deposition of the elements Sr, Mn, Fe and Mg which are tracers for soil and crustal dust implies land-clearing, mining and hauling emissions greatly impacted surrounding human settlements and ecosystems. Copyright © 2015 Elsevier Ltd. All rights reserved.

Cross-system nutrient transport: effects of locally-derived aeolian dust on oligotrophic lakes in West Greenland

NASA Astrophysics Data System (ADS)

Bullard, J. E.; Anderson, N. J.; McGowan, S.; Prater, C.; Watts, M.; Whitford, E.

2017-12-01

Terrestrially-derived nutrients can strongly affect production in aquatic environments. However, while some research has focused on nutrient delivery via hydrological inputs, the effects of atmospheric dry deposition are comparatively understudied. This paper examines the influence of aeolian-derived elements on water chemistry and microbial nutrient-limitation in oligotrophic lakes in West Greenland. Estimates of seasonal dust deposition and elemental leaching rates are combined with lake nutrient concentration measurements to establish the role of glacio-fluvial dust deposition in shaping nutrient stoichiometry of downwind lakes. The bioavailability of dust-associated elements is also explored using enzyme assays designed to indicate nutrient-limitation in microbial communities sampled across a dust deposition gradient. Together, these analyses demonstrate the importance of atmospheric dust inputs on hydrologically-isolated lakes found in arid high-latitude environments and demonstrate the need to better understand the role of aeolian deposition in cross-system nutrient transport.

Why do sand furrow distributions vary in the North Polar latitudes on Mars?

NASA Astrophysics Data System (ADS)

Bourke, Mary; McGaley-Towle, Zoe

2014-05-01

Sand dunes on Mars display geomorphic evidence of an active and dynamic sediment flux. Barchan dunes migrate, ripples move and the slipface morphology changes annually. Aeolian sediment transport is seasonally constrained and linked to cryogenic processes. Sand furrows are geomorphic features that are eroded into the surface of dunes. They form during sublimation of the seasonal carbon dioxide deposit which moves gas and sand through vents in the ice (cryo-venting) (Bourke, 2013). They are visible on the surface of dunes using the highest resolution images available for Mars. Previous work has noted that the distribution of furrows varies spatially both on individual dunes and at different Polar locations. Here we report on the preliminary findings of a mapping project that seeks to confirm this previous qualitative observation. In addition, we aim to explain the observed spatial and temporal variation in sand furrows on North Polar dunes. Ten polar sites that reflect a latitudinal range of 9.5º are being analysed. The HiRISE images were acquired between 16/2/2012 and 31/05/2012, over a period of 105 Earth days or 102 Sols. We have completed mapping of 1711 sand furrows in an 84 km2 area of sand dunes, i.e. at four of the ten sites. The data confirm that there is variability in the distribution of sand furrows in the Polar Region. While data from all ten sites will be required to fully test the assertion of a latitudinal control, it is worth noting that the two most northerly sites have a significantly higher density of furrows compared to the two lower latitude sites. As the seasonal ice thickness is known to increases pole-ward on Mars, our data suggest that effective furrow formation may be linked to ice deposit thickness. In particular, it suggests that a threshold in ice thickness must be crossed in order for effective cryo-venting to occur. Bourke, M.C., 2013. Sand Furrows: A new surface feature on Martian dunes, EGU, EGU2013-11859, Vienna.

The transitional depositional environment and sequence stratigraphy of Chasma Boreale

NASA Astrophysics Data System (ADS)

Brothers, S. C.; Kocurek, G.

2018-07-01

The depositional system within Chasma Boreale is unique in that it contains active aeolian environments, expressed as dune fields, and active cryosphere environments, present as layered ice deposits, as well as environments that transition between these. This work presents a new analysis of the Chasma Boreale sediment system that creates an interpretative framework addressing: (a) controls on the balance between aeolian and cryospheric processes in the modern depositional system, (b) the stratigraphic architecture of related sedimentary deposits, and (c) processes of sediment accumulation and preservation. Images from Context Camera (CTX; 6 m/pixel) are used to classify and map sedimentary environments, surfaces, and deposits on the reentrant floor, to refine the established geologic map of the reentrant, and to infer the stratigraphic record of the accumulation from Chasma Boreale's depositional system. A spectrum of sedimentary environments occurring between those dominated by aeolian and by cryospheric processes are identified. Through time, the boundaries of these sedimentary environments have shifted, resulting in complex lateral changes in the configuration of sedimentary environments on the reentrant's floor. Vertically, the stratigraphic record is characterized by the punctuation of sandy aeolian deposits by icy surfaces that indicate episodes of ice growth that preserve underlying deposits, resulting in accumulation. Stabilized icy surfaces occur at multiple vertical (temporal) scales and lateral extents, suggesting the influence of both regional climate change due to allogenic forcing, as well as autogenic dynamics within the transitional system. These observations demonstrate that the Chasma Boreale accumulation can be interpreted in an aeolian sequence stratigraphic framework. This work contributes the first detailed description of the processes forming polar aeolian sequences, with an emphasis on the competing and complementary dynamics between aeolian

A new turbulence-based model for sand transport

NASA Astrophysics Data System (ADS)

Mayaud, Jerome; Wiggs, Giles; Bailey, Richard

2016-04-01

Knowledge of the changing rate of sediment flux in space and time is essential for quantifying surface erosion and deposition in desert landscapes. While many aeolian studies have relied on time-averaged parameters such as wind velocity (U) and wind shear velocity (u*) to determine sediment flux, there is increasing evidence that high-frequency turbulence is an important driving force behind the entrainment and transport of sand. However, turbulence has yet to be incorporated into a functional sand transport model that can be used for predictive purposes. In this study we present a new transport model (the 'turbulence model') that accounts for high-frequency variations in the horizontal (u) and vertical (w) components of wind flow. The turbulence model is fitted to wind velocity and sediment transport data from a field experiment undertaken in Namibia's Skeleton Coast National Park, and its performance at three temporal resolutions (10 Hz, 1 Hz, 1 min) is compared to two existing models that rely on time-averaged wind velocity data (Radok, 1977; Dong et al., 2003). The validity of the three models is analysed under a variety of saltation conditions, using a 2-hour (1 Hz measurement resolution) dataset from the Skeleton Coast and a 5-hour (1 min measurement resolution) dataset from the southwestern Kalahari Desert. The turbulence model is shown to outperform the Radok and Dong models when predicting total saltation count over the three experimental periods. For all temporal resolutions presented in this study (10 Hz-10 min), the turbulence model predicted total saltation count to within at least 0.34%, whereas the Radok and Dong models over- or underestimated total count by up to 5.50% and 20.53% respectively. The strong performance of the turbulence model can be attributed to a lag in mass flux response built into its formulation, which can be adapted depending on the temporal resolution of investigation. This accounts for the inherent lag within the physical

The significance of discharge in the replenishment of sand bar deposits along the Colorado River through the Grand Canyon

NASA Astrophysics Data System (ADS)

Wiele, S.; Hazel, J.; Schmidt, J. C.; Melis, T.

2002-12-01

Topographic sandbar surveys, recovered scour chains, analysis of aerial photos, and modeling of sand deposition demonstrate that releases from Glen Canyon Dam greater than power-plant capacity (PPC; about 900 cubic meters per second) are significantly more effective than PPC-limited releases at redistributing sand from the channel bed to higher elevations along the channel margin. A release of 1,270 m3/s (1.4 times the PPC) for 7 days in 1996 tested the effectiveness with which sandbars could be restored by the manipulation of dam releases aimed at redistributing a limited sand supply. This high flow generally resulted in substantial increases in bar size, although some sandbars close to the dam eroded. Since 1996, releases for bar building and habitat maintenance (a 2-day release in 1997 and two 4-day releases in 2000) have been limited to PPC. Field measurements indicate that the 1996 release of 1,270 m3/s significantly increased the area and volume of sand deposits at elevations greater than the stage reached during typical post-dam flows. Minor aggradation occurred during the PPC flows. In 1996, the relative extent of erosion and deposition changed longitudinally downstream as evidenced by the area of substantial deposition exceeding that of erosion at sites further downstream. The number of bars that were substantially reworked, as measured by the number of bars that significantly increased or decreased in area at the elevation range of normal dam operations, was much greater at 1,270 m3/s than at 900 m3/s. Deposition from the 1,270 m3/s release persisted at many sites on a multi-year scale whereas deposition resulting from the PPC flows only lasted a few months. Minor deposition during PPC flows in 1997, however, was greatest in upstream reaches where bar erosion during normal flows had been more extensive. These observations show that deposition is sensitive to flow magnitude and depth of inundation as well as sand supply. Flow, sand transport, and bed

Ranking methodology for determining the relative favorability for commercial development of US tar-sand deposits

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aamodt, P.L.; Freiwald, J.G.

1983-03-01

As a part of the DOE's program to stimulate petroleum production from unconventional sources, the Los Alamos National Laboratory has developed a methodology to compare and rank tar sand deposits, based on their suitability for commercial development. Major categories influencing favorability were identified and evaluated to determine their individual and collective impacts. To facilitate their evaluation, deposit characteristics, extraction technologies, environmental controls, and institutional constraints were broken down into their elements. The elements were assessed singly and in interactive groups to determine their influence on favorability for commercial development. A numerical value was assigned each element to signify its estimatedmore » importance relative to the other elements. Eight tar sand deposits were evaluated using only one major category, deposit characteristics. This initial, and only partial favorability assessment, was solely a test of the methodology, and it was considered successful. Because only one of the four major categories was used for this initial favorability ranking, and also because the available deposit characteristic data were barely adequate for the test, these first results should be used only as an example of how the methodology is to be applied when more complete data are available. The eight deposits and their relative favorability rankings for commercial development, based only on the deposit characteristics, are Sunnyside, Utah; Asphalt Ridge, Utah; Edna, California; Santa Rosa, New Mexico; Tar Sand Triangle, Utah; PR Spring, Utah; Uvalde, Texas; and circle cliffs, Utah.« less

Aeolian Processes and the Biosphere

NASA Astrophysics Data System (ADS)

Ravi, Sujith; D'Odorico, Paolo; Breshears, David D.; Field, Jason P.; Goudie, Andrew S.; Huxman, Travis E.; Li, Junran; Okin, Gregory S.; Swap, Robert J.; Thomas, Andrew D.; Van Pelt, Scott; Whicker, Jeffrey J.; Zobeck, Ted M.

2011-08-01

Aeolian processes affect the biosphere in a wide variety of contexts, including landform evolution, biogeochemical cycles, regional climate, human health, and desertification. Collectively, research on aeolian processes and the biosphere is developing rapidly in many diverse and specialized areas, but integration of these recent advances is needed to better address management issues and to set future research priorities. Here we review recent literature on aeolian processes and their interactions with the biosphere, focusing on (1) geography of dust emissions, (2) impacts, interactions, and feedbacks, (3) drivers of dust emissions, and (4) methodological approaches. Geographically, dust emissions are highly spatially variable but also provide connectivity at global scales between sources and effects, with “hot spots” being of particular concern. Recent research reveals that aeolian processes have impacts, interactions, and feedbacks at a variety of scales, including large-scale dust transport and global biogeochemical cycles, climate mediated interactions between atmospheric dust and ecosystems, impacts on human health, impacts on agriculture, and interactions between aeolian processes and dryland vegetation. Aeolian dust emissions are driven largely by, in addition to climate, a combination of soil properties, soil moisture, vegetation and roughness, biological and physical crusts, and disturbances. Aeolian research methods span laboratory and field techniques, modeling, and remote sensing. Together these integrated perspectives on aeolian processes and the biosphere provide insights into management options and aid in identifying research priorities, both of which are increasingly important given that global climate models predict an increase in aridity in many dryland systems of the world.

Airflow Dynamics and Sand Transport over a Coastal Foredune with Large Woody Debris.

NASA Astrophysics Data System (ADS)

Grilliot, M. J.; Walker, I. J.; Bauer, B. O.

2016-12-01

Airflow dynamics and sand transport patterns over beach-foredune systems are complex due to the effects of topographic forcing and varied surface roughness elements. The role of large woody debris (LWD) as a roughness element in foredune dynamics is understudied compared to the effects of plant cover. Unlike plants, non-porous objects like LWD impose bluff body effects and induce secondary flow circulation that varies with LWD size, density, and arrangement. It is hypothesized that modified flow patterns over LWD can influence beach-dune sediment budgets and dune geometry via changes to mean near-surface flow patterns, turbulence, sand transport pathways and sedimentation patterns. In turn, LWD may act as an accretion anchor and store appreciable amounts of aeolian sand that subsequently may provide an enhanced buffer against coastal and/or wind erosion. This study examines turbulent airflow dynamics and related sand transport patterns for oblique onshore flow conditions over a mesotidal beach and scarped dune on Calvert Island, British Columbia, Canada. Abundant exposed LWD fronting the foredune enhances turbulent Reynolds stress (RS) and turbulence intensity (TI) near the surface. During low, yet competent wind speeds (6.54 m s-1), RS and TI are not competent enough in the sheltered flow regions within the LWD matrix and sediment deposition occurs. However, small zones of localized acceleration were observed with sand transport. Higher wind speeds, well above the entrainment threshold, increase RS and TI over LWD relative to the beach, facilitating sediment transport through and over the LWD matrix, with localized pockets of deposition in sheltered areas. The majority of LWD deposits on beaches in the region are anthropogenic logging debris and are known to be decreasing since the 1950s, but likely earlier. Thus, it is important to understand how non-porous roughness elements, like LWD, affect beach-dune sediment budgets and evolution, particularly in light of

The Influences of Geologic Depositional Environments on Sand Boil Development, Tara Wildlife Lodge Area in Mississippi

DTIC Science & Technology

2016-03-01

ER D C/ G SL T R- 16 -7 The Influences of Geologic Depositional Environments on Sand Boil Development, Tara Wildlife Lodge Area in...client/default. ERDC/GSL TR-16-7 March 2016 The Influences of Geologic Depositional Environments on Sand Boil Development, Tara Wildlife Lodge...Army Corps of Engineers Washington, DC 20314-1000 ERDC/GSL TR-16-7 ii Abstract A comprehensive study of the subsurface geology in the Tara Wildlife

Transverse Aeolian Ridges on Mars: Sediment sources, volumes, and ages.

NASA Astrophysics Data System (ADS)

Berman, D. C.; Balme, M. R.

2014-12-01

Transverse Aeolian Ridges (TARs) are aeolian bedforms that are morphologically and dimensionally distinct from Large Dark Dune (LDD) fields, being generally brighter than, or of similar albedo to, the surrounding terrain. These features are significantly smaller than the LDDs, appear to form normal to local winds, and tend to have simple, transverse, ripple-like morphologies. Whether these small martian bedforms represent large granule ripples, small transverse dunes, or something else entirely is currently under debate. The spatial distribution of TARs provides important information about where on Mars aeolian sediments are concentrated, and determining their volume can help us constrain the sediment transport regime on Mars. Also, if we can determine if TARs were active only in the past, or whether TARs are mobile under today's wind conditions, then we can begin to assess when and where TARs are/were active over Mars' recent geological history. Thus TARs have the potential for being indicators/records of climate change on Mars. In this work we build on previous work [1,2] and focus on the local/regional scale. We have identified six regional study areas, each 5° by 5°, to investigate the behavior of TARs in detail; one in the northern hemisphere, three in the equatorial band, and two in the southern hemisphere. We have systematically mapped TAR and LDD deposits in each study area to constrain sediment transport pathways and identify sediment sources. In general, TAR sediments appear to be tied to local sources such as LDDs or layered terrains. HiRISE DTMs were utilized to measure TAR heights, widths, wavelengths, and lengths to calculate sediment volumes and estimate volumes over entire study areas based on mapping. Crater count analyses on contiguous TAR fields in the equatorial regions, where the bedforms appear more lithified, reveal ages of several million years. Mid-latitude TAR fields do not show any superposed craters, suggesting much younger deposits

HIGH-ANGLE AEOLIAN CROSSBEDDING AT TRAIL RIDGE, FLORIDA.

USGS Publications Warehouse

Force, Eric; Garnar, Tom

1985-01-01

This paper described new evidence concerning the origin of the Trail Ridge mineral sands deposit in Florida. Rarely exposed sections of the orebody exhibit structures indicative of sand dune formation rather than coastal beach sand accumulation. The implications for mineral sands exploration, and therefore resources, in the southeastern USA are highlighted.

Continued monitoring of aeolian activity within Herschel Crater, Mars

NASA Astrophysics Data System (ADS)

Cardinale, Marco; Pozzobon, Riccardo; Michaels, Timothy; Bourke, Mary C.; Okubo, Chris H.; Chiara Tangari, Anna; Marinangeli, Lucia

2017-04-01

In this work, we study a dark dune field on the western side of Herschel crater, a 300 km diameter impact basin located near the Martian equator (14.4°S, 130°E), where the ripple and dune motion reflects the actual atmospheric wind conditions. We develop an integrated analysis using (1) automated ripple mapping that yields ripple orientations and evaluates the spatial variation of actual atmospheric wind conditions within the dunes, (2) an optical cross-correlation that allows us to quantify an average ripple migration rate of 0.42 m per Mars year, and (3) mesoscale climate modeling with which we compare the observed aeolian changes with modeled wind stresses and directions. Our observations are consistent with previous work [1] [2] that detected aeolian activity in the western part of the crater. It also demonstrates that not only are the westerly Herschel dunes movable, but that predominant winds from the north are able to keep the ripples and dunes active within most (if not all) of Herschel crater in the current atmospheric conditions. References: [1] Cardinale, M., Silvestro, S., Vaz, D.A., Michaels, T., Bourke, M.C., Komatsu, G., Marinangeli, L., 2016. Present-day aeolian activity in Herschel Crater, Mars. Icarus 265, 139-148. doi:10.1016/j.icarus.2015.10.022. [2] Runyon, K.D., Bridges, N.T., Ayoub, F., Newman, C.E. and Quade, J.J., 2017. An integrated model for dune morphology and sand fluxes on Mars. Earth and Planetary Science Letters, 457, pp.204-212.

Where on Earth can we find Mars? Characterization of an Aeolian Analogue in Northwestern Argentina

NASA Astrophysics Data System (ADS)

Favaro, E. A.; Hugenholtz, C.; Barchyn, T.

2017-12-01

The Puna Plateau of northwestern Argentina is as a promising analogue for Martian aeolian processes owing to its altitude, low atmospheric pressure, aridity, and widespread granular and bedrock aeolian features. The study was conducted in and surrounding the area known as the Campo de Piedra Pómez - a prominent expanse of wind-carved ignimbrite in Argentina's Catamarca Province. To interpret the evolution of this unique laboratory, which is limited by its isolated location and dearth of in situ measurements, we investigated contemporary aeolian sediment transport through a combination of modeled meteorological data, satellite imagery, field measurements, and sediment traps. Our objective is to utilize modeled meteorological data, satellite imagery, and field measurements and samples to characterize the aeolian environment here to base analogue studies. Satellite imagery from Terra MODIS, GeoEye, and Ikonos indicate recent large-scale aeolian sediment transport events and migration of gravel in the region. A prominent, region-wide sediment transport event on 14 August 2015 coincided with synoptic-scale pressure patterns indicating a strong Zonda (Foehn) winds. Sediment traps and marbles provide additional evidence of wind-driven transport of sand and gravel. Yet, despite the body of evidence for sediment transport on the Puna Plateau, modeled wind data from the European Center for Midrange Weather Forecasting suggest wind rarely attains the speeds necessary to initiate sediment transport. This disconnect is reminiscent of the Martian Saltation Paradox which suggested winds on Mars were incapable of mobilizing sediment, despite widespread evidence from rover, lander, and satellite observations. This raises questions about: (i) the suitability of modeled wind data for characterizing aeolian processes on both planets, and (ii) the possibility that most geomorphic work is conducted in extreme, but infrequent events in this region (possibly analogous to Mars). We

Aeolian Landscapes of Titan from Cassini RADAR Reveal Winds, Elevation Constraints and Sediment Characteristics

NASA Astrophysics Data System (ADS)

Radebaugh, J.; Lewis, R. C.; Bishop, B.; Christiansen, E. H.; Kerber, L.; Rodriguez, S.; Narteau, C.; Le Gall, A. A.; Lucas, A.; Malaska, M.

2017-12-01

Similar to terrestrial bodies with atmospheres, a significant portion of the surface of Titan is covered in aeolian landscapes, now imaged by Cassini RADAR at close to 50% coverage. While the compositions of the wind-carried and wind-carved sediments are under discussion, their characteristics, such as being rounded, loose and capable of being saltated, or being fine, soft and forming easily erodible deposits, can be discerned from the geomorphology. Large duneforms are similar to those in Earth's big deserts, formed by particles in strict size and shape limits, and steep, badlands-like morphologies of yardang regions indicate soft rocks with armored features. Shapes and orientations of dunes and yardangs can also reveal wind directions and effects of elevation and topographic obstacles. Recent studies of dunes in the Belet Sand Sea of Titan's equatorial trailing hemisphere reveal dunes are generally wider and with greater spacing near the center, similar to dunes in the Namib Sand Sea of Earth. Dune-to-interdune ratios decrease toward higher latitudes, as was previously observed, and are slightly higher in regions of low elevation, which may relate to elevation affecting winds and sand transport capacity. However, this relationship is not as strong for the Namib. Furthermore, the effects of the location of dunes with respect to sand sea margins on dune parameter values has only begun to be explored. The European ERA-Interim (observations plus model) wind results for the Namib reveal vector sum winds are several degrees away from down the dune long axis, consistent with the fingering mode of dune growth, and allowing for down-axis sand transport. We assume similar model winds for the dunes of Titan. Model winds for the yardangs of the Lut desert of Earth are directly down axis, which means wind directions should be able to be determined in the isolated yardang fields of Titan's northern midlatitudes. Further studies of dune parameters on Titan from Cassini can help

High-Altitude Aeolian Research on the Tibetan Plateau

NASA Astrophysics Data System (ADS)

Dong, Zhibao; Hu, Guangyin; Qian, Guangqiang; Lu, Junfeng; Zhang, Zhengcai; Luo, Wanyin; Lyu, Ping

2017-12-01

Aeolian processes and their role in desertification have been studied extensively at low elevations but have been rarely studied at high elevations in areas such as the Tibetan Plateau, where aeolian processes were active in the geologic past and remain active today. In this review, we summarize research that improves our understanding of aeolian processes on the Tibetan Plateau, including the distribution, characteristics, and provenance of aeolian sediments; the history of aeolian activity; aeolian geomorphology; and wind-driven land degradation. Contemporary aeolian processes primarily occur in dry basins, in wide river valleys, on lakeshores, on mountain slopes, and on gravel pavements. Sediment characteristics suggest a local origin and provide interesting contrasts with those of China's Loess Plateau. The history of aeolian activity and its paleoclimatic implications, reconstructed based on aeolian archives, is short (mostly since the Late Glacial) and shows wide regional differences. Aeolian geomorphology is simple and suggests short formation time. Wind-driven land degradation is less severe than previously thought, driven by different factors in different areas, and exhibited complex interactions with freeze-thaw processes. Aeolian research has been conducted within the general framework of aeolian science but addresses issues specific to the Tibetan Plateau that arise due to the low air temperature, low air density, and the presence of a cryosphere. We propose six priorities for future research: aeolian physics, the effect of freeze-thaw cycles, comparisons with other areas, regional differences, effects of wind-driven land degradation, and integrated observation and monitoring.

Incident angle of saltating particles in wind-blown sand.

PubMed

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

2013-01-01

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

Physical abrasion of mafic minerals and basalt grains: application to Martian aeolian deposits

USGS Publications Warehouse

Cornwall, Carin; Bandfield, Joshua L.; Titus, Timothy N.; Schreiber, B. C.; Montgomery, D.R.

2015-01-01

Sediment maturity, or the mineralogical and physical characterization of sediment deposits, has been used to locate sediment source, transport medium and distance, weathering processes, and paleoenvironments on Earth. Mature terrestrial sands are dominated by quartz, which is abundant in source lithologies on Earth and is physically and chemically stable under a wide range of conditions. Immature sands, such as those rich in feldspars or mafic minerals, are composed of grains that are easily physically weathered and highly susceptible to chemical weathering. On Mars, which is predominately mafic in composition, terrestrial standards of sediment maturity are not applicable. In addition, the martian climate today is cold, dry and sediments are likely to be heavily influenced by physical weathering rather than chemical weathering. Due to these large differences in weathering processes and composition, martian sediments require an alternate maturity index. Abrason tests have been conducted on a variety of mafic materials and results suggest that mature martian sediments may be composed of well sorted, well rounded, spherical basalt grains. In addition, any volcanic glass present is likely to persist in a mechanical weathering environment while chemically altered products are likely to be winnowed away. A modified sediment maturity index is proposed that can be used in future studies to constrain sediment source, paleoclimate, mechanisms for sediment production, and surface evolution. This maturity index may also provide details about erosional and sediment transport systems and preservation processes of layered deposits.

Aeolian system dynamics derived from thermal infrared data

NASA Astrophysics Data System (ADS)

Scheidt, Stephen Paul

Thermal infrared (TIR) remote-sensing and field-based observations were used to study aeolian systems, specifically sand transport pathways, dust emission sources and Saharan atmospheric dust. A method was developed for generating seamless and radiometrically accurate mosaics of thermal infrared data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument. Using a combination of high resolution thermal emission spectroscopy results of sand samples and mosaic satellite data, surface emissivity was derived to map surface composition, which led to improvement in the understanding of sand accumulation in the Gran Desierto of northern Sonora, Mexico. These methods were also used to map sand transport pathways in the Sahara Desert, where the interaction between sand saltation and dust emission sources was explored. The characteristics and dynamics of dust sources were studied at White Sands, NM and in the Sahara Desert. At White Sands, an application was developed for studying the response of dust sources to surface soil moisture based on the relationship between soil moisture, apparent thermal inertia and the erosion potential of dust sources. The dynamics of dust sources and the interaction with sand transport pathways were also studied, focusing on the Bodele Depression of Chad and large dust sources in Mali and Mauritania. A dust detection algorithm was developed using ASTER data, and the spectral emissivity of observed atmospheric dust was related to the dust source area in the Sahara. At the Atmospheric Observatory (IZO) in Tenerife, Spain where direct measurement of the Saharan Air Layer could be made, the cycle of dust events occurring in July 2009 were examined. From the observation tower at the IZO, measurements of emitted longwave atmospheric radiance in the TIR wavelength region were made using a Forward Looking Infrared Radiometer (FLIR) handheld camera. The use of the FLIR to study atmospheric dust from the Saharan is a

Sedimentary processes associated with sand and boulder deposits formed by the 2011 Tohoku-oki tsunami at Sabusawa Island, Japan

NASA Astrophysics Data System (ADS)

Goto, Kazuhisa; Sugawara, Daisuke; Ikema, Satoko; Miyagi, Toyohiko

2012-12-01

This paper reports on the sedimentary processes of sand and boulder deposition at Sabusawa Island, Japan as a result of the 2011 Tohoku-oki tsunami. Boulders were composed of tuffaceous rocks and sourced from an earthquake-triggered slope failure as well as concrete fragments of seawall. They were scattered over the ground surface and did not form boulder ridges, although there was some local imbrication. The boulders were deposited on top of a sand layer indicating that the latter, possibly deposited from bed load, covered the ground surface first. This sand layer probably reduced friction allowing boulders to be transported more easily than might be expected across a hard ground with a high bottom friction. Sand deposits showed landward thinning and fining features, while the boulders showed a landward coarsening (tuffaceous boulders) or a landward fining (concrete boulders), indicating that large clasts were not necessarily scattered randomly but rather might have a clast size gradient with distance inland. These features are explained by the local topographic setting that constrained the directions of incoming and returning tsunami flows. Some clasts at the inland extent of the boulder field were covered by an upward fining sand layer. This feature suggests that the boulders were deposited prior to the suspended sands, with the latter subsequently laid down before the water level dropped below the top of the boulders. Such modern investigations of the sedimentary features of various sizes of grains and clasts immediately after a tsunami provide invaluable data for the reconstruction of inundation processes.

Abundances and implications of volatile-bearing species from evolved gas analysis of the Rocknest aeolian deposit, Gale Crater, Mars

NASA Astrophysics Data System (ADS)

Archer, Paul Douglas; Franz, Heather B.; Sutter, Brad; Arevalo, Ricardo D.; Coll, Patrice; Eigenbrode, Jennifer L.; Glavin, Daniel P.; Jones, John J.; Leshin, Laurie A.; Mahaffy, Paul R.; McAdam, Amy C.; McKay, Christopher P.; Ming, Douglas W.; Morris, Richard V.; Navarro-González, Rafael; Niles, Paul B.; Pavlov, Alex; Squyres, Steven W.; Stern, Jennifer C.; Steele, Andrew; Wray, James J.

2014-01-01

The Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory (MSL) rover Curiosity detected evolved gases during thermal analysis of soil samples from the Rocknest aeolian deposit in Gale Crater. Major species detected (in order of decreasing molar abundance) were H2O, SO2, CO2, and O2, all at the µmol level, with HCl, H2S, NH3, NO, and HCN present at the tens to hundreds of nmol level. We compute weight % numbers for the major gases evolved by assuming a likely source and calculate abundances between 0.5 and 3 wt.%. The evolution of these gases implies the presence of both oxidized (perchlorates) and reduced (sulfides or H-bearing) species as well as minerals formed under alkaline (carbonates) and possibly acidic (sulfates) conditions. Possible source phases in the Rocknest material are hydrated amorphous material, minor clay minerals, and hydrated perchlorate salts (all potential H2O sources), carbonates (CO2), perchlorates (O2 and HCl), and potential N-bearing materials (e.g., Martian nitrates, terrestrial or Martian nitrogenated organics, ammonium salts) that evolve NH3, NO, and/or HCN. We conclude that Rocknest materials are a physical mixture in chemical disequilibrium, consistent with aeolian mixing, and that although weathering is not extensive, it may be ongoing even under current Martian surface conditions.

Beach-dune dynamics: Spatio-temporal patterns of aeolian sediment transport under complex offshore airflow

NASA Astrophysics Data System (ADS)

Lynch, K.; Jackson, D.; Delgado-Fernandez, I.; Cooper, J. A.; Baas, A. C.; Beyers, M.

2010-12-01

This study examines sand transport and wind speed across a beach at Magilligan Strand, Northern Ireland, under offshore wind conditions. Traditionally the offshore component of local wind regimes has been ignored when quantifying beach-dune sediment budgets, with the sheltering effect of the foredune assumed to prohibit grain entrainment on the adjoining beach. Recent investigations of secondary airflow patterns over coastal dunes have suggested this may not be the case, that the turbulent nature of the airflow in these zones enhances sediment transport potential. Beach sediment may be delivered to the dune toe by re-circulating eddies under offshore winds in coastal areas, which may explain much of the dynamics of aeolian dunes on coasts where the dominant wind direction is offshore. The present study investigated aeolian sediment transport patterns under an offshore wind event. Empirical data were collected using load cell traps, for aeolian sediment transport, co-located with 3-D ultrasonic anemometers. The instrument positioning on the sub-aerial beach was informed by prior analysis of the airflow patterns using computational fluid dynamics. The array covered a total beach area of 90 m alongshore by 65 m cross-shore from the dune crest. Results confirm that sediment transport occurred in the ‘sheltered’ area under offshore winds. Over short time and space scales the nature of the transport is highly complex; however, preferential zones for sand entrainment may be identified. Alongshore spatial heterogeneity of sediment transport seems to show a relationship to undulations in the dune crest, while temporal and spatial variations may also be related to the position of the airflow reattachment zone. These results highlight the important feedbacks between flow characteristics and transport in a complex three dimensional surface.

A 37,000-year environmental magnetic record of aeolian dust deposition from Burial Lake, Arctic Alaska

NASA Astrophysics Data System (ADS)

Dorfman, J. M.; Stoner, J. S.; Finkenbinder, M. S.; Abbott, M. B.; Xuan, C.; St-Onge, G.

2015-11-01

Environmental magnetism and radiocarbon dating of Burial Lake sediments constrain the timing and magnitude of regional aeolian deposition for the Noatak region of western Arctic Alaska for the last ∼37,000 years. Burial Lake (68.43°N, 159.17°W, 21.5 m water depth) is optimally located to monitor regional dust deposition because it is perched above local drainage and isolated from glacial processes. Cores collected in the summer of 2010 were studied through the application of magnetizations and progressive alternating field (AF) demagnetization of u-channel samples, with additional data provided by computed tomography (CT) derived density, hysteresis measurements, isothermal remanent magnetization (IRM) acquisition experiments, organic carbon content, biogenic silica, physical grain size, radiocarbon dating of wood, seeds, and plant macrofossils, point source magnetic susceptibility, and X-ray fluorescence (XRF). With similar magnetic properties to regional Alaskan loess deposits, low coercivity, highly magnetic material deposited during the late-Pleistocene contrasts with a high coercivity, weakly magnetic component found throughout the record, consistent with locally-derived detritus. The relative proportion of low coercivity to high coercivity magnetic material, defined by the S-Ratios, is used to reconstruct the regional input of dust to the basin over time. A four-fold decrease in the low coercivity component through the deglacial transition is interpreted to reflect diminished dust input to the region. Comparisons with potential sources of dust show that the timing of deposition in Burial Lake is largely consistent with general aridity, lack of vegetative cover, and increased windiness, rather than glacial advances or retreats. The influence from subaerial exposure of continental shelves cannot be ruled out as a significant far-field source of dust to interior Alaska during the Last Glacial Maximum (LGM), but is unlikely to have been the sole source, or to

Quantifying the provenance of aeolian sediments using multiple composite fingerprints

NASA Astrophysics Data System (ADS)

Liu, Benli; Niu, Qinghe; Qu, Jianjun; Zu, Ruiping

2016-09-01

We introduce a new fingerprinting method that uses multiple composite fingerprints for studies of aeolian sediment provenance. We used this method to quantify the provenance of sediments on both sides of the Qinghai-Tibetan Railway (QTR) in the Cuona Lake section of the Tibetan Plateau (TP), in an environment characterized by aeolian and fluvial interactions. The method involves repeatedly solving a linear mixing model based on mass conservation; the model is not limited to spatial scale or transport types and uses all the tracer groups that passed the range check, Kruskal-Wallis H-test, and a strict analytical solution screening. The proportional estimates that result from using different composite fingerprints are highly variable; however, the average of these fingerprints has a greater accuracy and certainty than any single fingerprint. The results show that sand from the lake beach, hilly surface, and gullies contribute, respectively, 48%, 31% and 21% to the western railway sediments and 43%, 33% and 24% to the eastern railway sediments. The difference between contributions from various sources on either side of the railway, which may increase in the future, was clearly related to variations in local transport characteristics, a conclusion that is supported by grain size analysis. The construction of the QTR changed the local cycling of materials, and the difference in provenance between the sediments that are separated by the railway reflects the changed sedimentary conditions on either side of the railway. The effectiveness of this method suggests that it will be useful in other studies of aeolian sediments.

Incident Angle of Saltating Particles in Wind-Blown Sand

PubMed Central

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

2013-01-01

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

Event sand layers suggesting the possibility of tsunami deposits identified in the upper Holocene sequence nearby the Kuwana fault, central Japan

NASA Astrophysics Data System (ADS)

Niwa, Y.; Sugai, T.; Matsuzaki, H.

2012-12-01

The Kuwana fault is located on coastal area situated on inner part of the Ise Bay, central Japan, which opens to the Nankai Trough. This reverse fault displaces a late Pleistocene terrace surface with 1 to 2 mm/yr of average vertical slip rate, and a topset of delta at several meters, respectively. And, this fault is estimated to have generated two historical earthquakes (the AD 745 Tempyo and the AD 1586 Tensho earthquakes). We identified two event sand layers from upper Holocene sequence on the upthrown side of the Kuwana fault. Upper Holocene deposits in this study area show prograding delta sequence; prodelta mud, delta front sandy silt to sand, and flood plain sand/mud, respectively, from lower to upper. Two sand layers intervene in delta front sandy silt layer, respectively. Lower sand layer (S1) shows upward-coarsening succession, whereas upper sand layer (S2) upward-fining succession. These sand layers contain sharp contact, rip-up crust, and shell fragment, indicating strong stream flow. Radiocarbon ages show that these strong stream flow events occurred between 3000 and 1600 years ago. Decreasing of salinity is estimated from decreasing trend of electrical conductivity (EC) across S1. Based on the possibility that decreasing of salinity can be occurred by shallowing of water depth caused by coseismic uplift, and that S1 can be correlated with previously known faulting event on the Kuwana fault, S1 is considered to be tsunami deposits caused by faulting on the Kuwana fault. On the other hand, S2, which cannot be correlated with previously known faulting events on the Kuwana fault, may be tsunami deposits by ocean-trench earthquake or storm deposits. In the presentation, we will discuss more detail correlation of these sand deposits not only in the upthrown side of the Kuwana fault, but also downthrown side of the fault.

Fluvial channel-belts, floodbasins, and aeolian ergs in the Precambrian Meall Dearg Formation (Torridonian of Scotland): Inferring climate regimes from pre-vegetation clastic rock records

NASA Astrophysics Data System (ADS)

Lebeau, Lorraine E.; Ielpi, Alessandro

2017-07-01

The interpretation of climate regimes from facies analysis of Precambrian clastic rocks has been challenging thus far, hindering full reconstructions of landscape dynamics in pre-vegetation environments. Yet, comparisons between different and co-active sedimentary realms, including fluvial-channelised, floodplain, and aeolian hold the potential to shed further light on this thematic. This research discusses a fluvial-aeolian record from the 1.2 Ga Meall Dearg Formation, part of the classic Torridonian succession of Scotland. Tentatively considered to date as a braided-fluvial deposit, this unit is here reappraised as the record of fluvial channel-belts, floodbasins, and aeolian ergs. Fluvial deposits with abundant transitional- to upper-flow regime structures (mostly cross-beds with tangential sets and plane/antidunal beds) and simple, low-relief sediment bars indicate a low-sinuosity, ephemeral style. Floodbasin deposits consist of plane and cross-beds ubiquitously bounded by symmetrical ripples, and rare sediment bars related to the progradation of splay complexes in temporary flooded depressions. Aeolian deposits occur nearby basement topography, and are dominated by large-scale, pin-stripe laminated cross-beds, indicative of intermountain ergs. Neither ephemeral-fluvial nor intermountain aeolian systems can be considered as reliable indicators of local climate, since their sedimentary style is respectively controlled by catchment size and shape, and basin topography relative to groundwater tables. Contrarily, the occurrence of purely clastic - rather than carbonate or evaporitic - floodplain strata can be more confidently related to humid regimes. In brief, this study provides new insight into an overlooked portion of the Torridonian succession of Scotland, and discusses climate inferences for Precambrian clastic terrestrial rocks.

Multi-Resolution Analysis of LiDAR data for Characterizing a Stabilized Aeolian Landscape in South Texas

NASA Astrophysics Data System (ADS)

Barrineau, C. P.; Dobreva, I. D.; Bishop, M. P.; Houser, C.

2014-12-01

Aeolian systems are ideal natural laboratories for examining self-organization in patterned landscapes, as certain wind regimes generate certain morphologies. Topographic information and scale dependent analysis offer the opportunity to study such systems and characterize process-form relationships. A statistically based methodology for differentiating aeolian features would enable the quantitative association of certain surface characteristics with certain morphodynamic regimes. We conducted a multi-resolution analysis of LiDAR elevation data to assess scale-dependent morphometric variations in an aeolian landscape in South Texas. For each pixel, mean elevation values are calculated along concentric circles moving outward at 100-meter intervals (i.e. 500 m, 600 m, 700 m from pixel). The calculated average elevation values plotted against distance from the pixel of interest as curves are used to differentiate multi-scalar variations in elevation across the landscape. In this case, it is hypothesized these curves may be used to quantitatively differentiate certain morphometries from others like a spectral signature may be used to classify paved surfaces from natural vegetation, for example. After generating multi-resolution curves for all the pixels in a selected area of interest (AOI), a Principal Components Analysis is used to highlight commonalities and singularities between generated curves from pixels across the AOI. Our findings suggest that the resulting components could be used for identification of discrete aeolian features like open sands, trailing ridges and active dune crests, and, in particular, zones of deflation. This new approach to landscape characterization not only works to mitigate bias introduced when researchers must select training pixels for morphometric investigations, but can also reveal patterning in aeolian landscapes that would not be as obvious without quantitative characterization.

Predictability of dune activity in real dune fields under unidirectional wind regimes

NASA Astrophysics Data System (ADS)

Barchyn, Thomas E.; Hugenholtz, Chris H.

2015-02-01

We present an analysis of 10 dune fields to test a model-derived hypothesis of dune field activity. The hypothesis suggests that a quantifiable threshold exists for stabilization in unidirectional wind regimes: active dunes have slipface deposition rates that exceed the vegetation deposition tolerance, and stabilizing dunes have the opposite. We quantified aeolian sand flux, slipface geometry, and vegetation deposition tolerance to directly test the hypothesis at four dune fields (Bigstick, White Sands Stable, White Sands Active, and Cape Cod). We indirectly tested the hypothesis at six additional dune fields with limited vegetation data (Hanford, Año Nuevo, Skagen Odde, Salton Sea, Oceano Stable, and Oceano Active, "inverse calculation sites"). We used digital topographic data and estimates of aeolian sand flux to approximate the slipface deposition rates prior to stabilization. Results revealed a distinct, quantifiable, and consistent pattern despite diverse environmental conditions: the modal peak of prestabilization slipface deposition rates was 80% of the vegetation deposition tolerance at stabilized or stabilizing dune fields. Results from inverse calculation sites indicate deposition rates at stabilized sites were near a hypothesized maximum vegetation deposition tolerance (1 m a-1), and active sites had slipface deposition rates much higher. Overall, these results confirm the hypothesis and provide evidence of a globally applicable, simple, and previously unidentified predictor for the dynamics of vegetation cover in dune fields under unidirectional wind regimes.

Paleo-Environment and C-14 Dating: The Key to the Depositional Age of the Tha Chang and Related Sand Pits, Northeastern Thailand

NASA Technical Reports Server (NTRS)

Putthapiban, P.; Zolensky, M.; Jull, T.; Demartino, M.; Salyapongse, S.

2012-01-01

Tha Chang sand pits, Nakhon Ratchasima Province and many other sand pits in the area adjacent to the Mun River are characterized by their fluviatile environment in association with mass wasting deposits, along the paleo-river channel and the flood plain of the Mun River. Sediments of these deposits are characterized by clasts of various rock types especially the resistant ones with frequent big tree trunks, logs and wood fragments in different sizes and various stages of transformation from moldering stage to lignification and petrification. Widespread pyritization of the lower horizon suggests strongly reducing environment during burial. The Tha Chang deposits have been received much attention from geoscientists especially paleontologist communities, as they contain fragments of some distinct vertebrate species such as Stegadon sp., hominoid primate, rhinoceros Aceratherium and others. Based on the associated mammal fauna and hominoid fossils, the late Miocene ( 9 - 6 Ma) was given for the time of deposition of this sand and gravel unit. Some other reports believed that sediments and materials of these sand and gravel quarries (pits) were deposited by high-energy flood pulses contemporaneous with the tektites forming event during mid-Pleistocene at c. 0.8 Ma. Interpretation from Palynostratigraphical study suggested that the lower horizon of Tha Chang sand pit was deposited during Pliocene/Pleistocene period and the upper horizons are Pleistoncene/Holocene. It is crystal clear that all the fluviatile sediments including tektites and almost all fossil fragments being deposited in these sand pits were, likely a multiple times reworked materials. Only some old bamboo trees, some old crowling trees and fossils grasses observed on the old river bank are considered in situ. C-14 dating of 5 old wood specimens from Tha Chang Sand Pits, 15 old wood specimens from Chumpuang Sand Pits and one sample of old pottery from a Chumpuang Sand Pit were carried out in the NSF

Atmospheric dust in modern soil on aeolian sandstone, Colorado Plateau (USA): Variation with landscape position and contribution to potential plant nutrients

USGS Publications Warehouse

Reynolds, R.; Neff, J.; Reheis, M.; Lamothe, P.

2006-01-01

Rock-derived nutrients in soils originate from both local bedrock and atmospheric dust, including dust from far-distant sources. Distinction between fine particles derived from local bedrock and from dust provides better understanding of the landscape-scale distribution and abundance of soil nutrients. Sandy surficial deposits over dominantly sandstone substrates, covering vast upland areas of the central Colorado Plateau, typically contain 5-40% silt plus clay, depending on geomorphic setting and slope (excluding drainages and depressions). Aeolian dust in these deposits is indicated by the presence of titanium-bearing magnetite grains that are absent in the sedimentary rocks of the region. Thus, contents of far-traveled aeolian dust can be estimated from magnetic properties that primarily reflect magnetite content, such as isothermal remanent magnetization (IRM). Isothermal remanent magnetization was measured on bulk sediment samples taken along two transects in surficial sediment down gentle slopes away from sandstone headwalls. One transect was in undisturbed surficial sediment, the other in a setting that was grazed by domestic livestock until 1974. Calculation of far-traveled dust contents of the surficial deposits is based on measurements of the magnetic properties of rock, surficial deposits, and modern dust using a binary mixing model. At the undisturbed site, IRM-based calculations show a systematic down-slope increase in aeolian dust (ranging from 2% to 18% of the surface soil mass), similar to the down-slope increase in total fines (18-39% of surface soil mass). A combination of winnowing by wind during the past and down-slope movement of sediment likely accounts for the modern distribution of aeolian dust and associated nutrients. At the previously grazed site, dust also increases down slope (5-11%) in sediment with corresponding abundances of 13-25% fines. Estimates of the contributions of aeolian dust to the total soil nutrients range widely

Coastal deposits of heavy mineral sands; Global significance and US resources

USGS Publications Warehouse

Van Gosen, Bradley S.; Bleiwas, Donald I.; Bedinger, George M.; Ellefsen, Karl J.; Shah, Anjana K.

2016-01-01

Ancient and modern coastal deposits of heavy mineral sands (HMS) are the principal source of several heavy industrial minerals, with mining and processing operations on every continent except Antarctica. For example, HMS deposits are the main source of titanium feedstock for the titanium dioxide (TiO2) pigments industry, obtained from the minerals ilmenite (Fe2+TiO3), rutile (TiO2) and leucoxene (an alteration product of ilmenite). HMS deposits are also the principal source of zircon (ZrSiO4), from which zirconium dioxide (ZrO2) is obtained for uses mostly in refractory products. Sometimes monazite [(Ce,La,Nd,Th)PO4] is recovered as a byproduct mineral, sought for its rare earth elements and thorium (Ault and others, 2016; Sengupta and Van Gosen, 2016; Van Gosen and Tulsidas, 2016). 

Cordão Formation: loess deposits in the southern coastal plain of the state of Rio Grande do Sul, Brazil.

PubMed

Lopes, Renato P; Dillenburg, Sergio R; Schultz, Cesar L

2016-01-01

Loess consists of silt-dominated sediments that cover ~10% of the Earth's surface. In southern South America it occurs in Argentina, Bolivia, Paraguay and Uruguay, and its presence in southern Brazil was never studied in detail. Here is proposed a new lithostratigraphic unit, Cordão Formation, consisting of loess deposits in the southern Brazilian coastal plain. It consists of fine-very fine silt with subordinate sand and clay, found mostly in lowland areas between Pleistocene coastal barriers. These sediments are pale-colored (10YR hue) and forms ~1,5-2,0 meter-thick stable vertical walls. The clay minerals include illite, smectite, interstratified illite/smectite and kaolinite, the coarser fraction is mostly quartz and plagioclase. Caliche and iron-manganese nodules are also present. The only fossils found so far are rodent teeth and a tooth of a camelid (Hemiauchenia paradoxa). Luminescence ages indicate that this loess was deposited in the latest Pleistocene, between ~30 and 10 kyrs ago, and its upper portion was modified by erosion and accumulation of clay and organic matter in the Holocene. The estimated accumulation rate was ~630 g/m2/year. The probable source of this loess is the Pampean Aeolian System of Argentina and it would have been deposited by the increased aeolian processes of the last glacial.

Highstand shelf fans: The role of buoyancy reversal in the deposition of a new type of shelf sand body

USGS Publications Warehouse

Steel, Elisabeth; Simms, Alexander R.; Warrick, Jonathan; Yokoyama, Yusuke

2016-01-01

Although sea-level highstands are typically associated with sediment-starved continental shelves, high sea level does not hinder major river floods. Turbidity currents generated by plunging of sediment-laden rivers at the fluvial-marine interface, known as hyperpycnal flows, allow for cross-shelf transport of suspended sand beyond the coastline. Hyperpycnal flows in southern California have deposited six subaqueous fans on the shelf of the northern Santa Barbara Channel in the Holocene. Using eight cores and nine grab samples, we describe the deposits, age, and stratigraphic architecture of two fans in the Santa Barbara Channel. Fan lobes have up to 3 m of relief and are composed of multiple hyperpycnite beds ∼5 cm to 40 cm thick. Deposit architecture and geometry suggest the hyperpycnal flows became positively buoyant and lifted off the seabed, resulting in well-sorted, structureless, elongate sand lobes. Contrary to conventional sequence stratigraphic models, the presence of these features on the continental shelf suggests that active-margin shelves may locally develop high-quality reservoir sand bodies during sea-level highstands, and that such shelves need not be solely the site of sediment bypass. These deposits may provide a Quaternary analogue to many well-sorted sand bodies in the rock record that are interpreted as turbidites but lack typical Bouma-type features.

Approach to Assessing the Effects of Aerial Deposition on Water Quality in the Alberta Oil Sands Region.

PubMed

Dayyani, Shadi; Daly, Gillian; Vandenberg, Jerry

2016-02-01

Snow cover forms a porous medium that acts as a receptor for aerially deposited polycyclic aromatic hydrocarbons (PAHs) and metals. The snowpack, acting as a temporary storage reservoir, releases contaminants accumulating over the winter during a relatively short melt period. This process could result in elevated concentrations of contaminants in melt water. Recent studies in the Alberta oil sands region have documented increases in snowpack and lake sediment concentrations; however, no studies have addressed the fate and transport of contaminants during the snowmelt period. This study describes modelling approaches that were developed to assess potential effects of aerially deposited PAHs and metals to snowpack and snowmelt water concentrations. The contribution of snowmelt to freshwater PAH concentrations is assessed using a dynamic, multi-compartmental fate model, and the contribution to metal concentrations is estimated using a mass-balance approach. The modelling approaches described herein were applied to two watersheds in the Alberta oil sands region for two planned oil sands developments. Accumulation of PAHs in a lake within the deposition zone was also modelled for comparison to observed concentrations.

Central Asian sand seas climate change as inferred from OSL dating

NASA Astrophysics Data System (ADS)

Maman, Shimrit; Tsoar, Haim; Blumberg, Dan; Porat, Naomi

2014-05-01

Luminescence dating techniques have become more accessible, widespread, more accurate and support studies of climate change. Optically stimulated luminescence (OSL) is used to determine the time elapsed since quartz grains were last exposed to sunlight, before they were buried and the dune stabilized. Many sand seas have been dated extensively by luminescence, e.g., the Kalahari, Namib the Australian linear dunes and the northwestern Negev dune field, Israel. However, no ages were published so far from the central Asian sand seas. The lack of dune stratigraphy and numerical ages precluded any reliable assessment of the paleoclimatic significance of dunes in central Asia. Central Asian Sand seas (ergs) have accumulated in the Turan basin, north-west of the Hindu Kush range, and span from south Turkmenistan to the Syr-Darya River in Kazakhstan. These ergs are dissected by the Amu-Darya River; to its north lies the Kyzylkum (red sands) and to its south lies the Karakum (black sands). Combined, they form one of the largest sand seas in the world. This area is understudied, and little information has been published regarding the sands stabilization processes and deposition ages. In this study, OSL ages for the Karakum and Kyzylkum sands are presented and analysis of the implications of these results is provided. Optical dates obtained in this study are used to study the effects climatic changes had on the mobility and stability of the central Asian sand seas. Optically stimulated luminescence ages derived from the upper meter of the interdune of 14 exposed sections from both ergs, indicate extensive sand and dune stabilization during the mid-Holocene. This stabilization is understood to reflect a transition to a warmer, wetter, and less windy climate that generally persisted until today. The OSL ages, coupled with a compilation of regional paleoclimatic data, corroborate and reinforce the previously proposed Mid-Holocene Liavliakan phase, known to reflect a warmer

Palaeoclimatic implications of aeolian sediments on the Miaodao Islands, Bohai Sea, East China, based on OSL dating and proxies

NASA Astrophysics Data System (ADS)

Xu, Shujian; Ding, Xinchao; Yu, Lupeng; Ni, Zhichao

2015-12-01

The loess-paleosol sequences in Shandong Province, East China, is an important aeolian archive, which can provide information for aeolian activity, palaeoclimatic change and sea level change in eastern coast of China since the last interglacial period. However, for so long, most of the studies about loess have been focused on the Chinese Loess Plateau, remaining many questions and disputes about the loess in East China. The Xianjingyuan (XJY) section on the TIA, Bohai Sea, is a representative aeolian section for islands off the eastern coast of China. In this study, optically stimulated luminescence (OSL) dating, particle size and magnetic susceptibility were applied to date and analysis the loess-paleosol sequences in this section. The results show that: (1) The OSL ages at the depths of 0.8 m, 2.5 m, and 3.9 m are 12.6 ± 1.0 ka, 19.2 ± 1.1 ka and 56.9 ± 2.6 ka, respectively, and the loess started to accumulate at ca. 86.5 ka according to the depositional rates (2) The loess accumulated mainly during the Marine Isotope Stage (MIS) 2, i.e., Last glacial maximum and deglaciation, MIS4 and MIS3b with higher depositional rate, coarser grain size, and higher magnetic susceptibility; while paleosol mainly developed during MIS3a, MIS3c and MIS5 with lower depositional rate, finer grain size and lower magnetic susceptibility. (3) The palaeoclimatic changes and aeolian sediments evolution were mainly controlled by the changes of East Asian summer monsoon and sea levels.

Discovery of a landscape-wide drape of late-glacial aeolian silt in the western Northern Calcareous Alps (Austria): First results and implications

NASA Astrophysics Data System (ADS)

Gild, Charlotte; Geitner, Clemens; Sanders, Diethard

2018-01-01

Aeolian deposits record palaeoenvironmental conditions and may coin soil properties. Whereas periglacial loess is extensively investigated for 200 years, the study of the intramontane wind-blown deposits of the Alps has just stuttered along. Herein, we describe a drape of polymictic siliciclastic silt interpreted as an aeolian deposit that veneers extensive areas in the western Northern Calcareous Alps (NCA), from kames terraces near valley floors up to last-glacial nunataks. The NCA - part of the Eastern Alps mountain range - consist mainly of Triassic carbonate rocks; these are overlain by deposits of the Last Glacial Maximum (LGM) and its deglacial-paraglacial aftermath (e.g., glacial tills, fluvio-lacustrine successions, alluvial fans, scree slopes) - and a regional drape of polymictic silt newly described herein. The drape is typically a few decimeters in thickness and slightly modified by soil formation; it consists mainly of well-sorted silt of quartz, feldspars, phyllosilicates (muscovite, chlorite, biotite), amphiboles and, rarely, calcite or dolomite. The drape is unrelated to the substrate: it overlies carbonate bedrock and - in lateral continuity - abandoned deposystems such as colluvial slopes of redeposited till, kames, alluvial fans, scree slopes, and rock avalanche deposits. The drape was spotted from near the present valley floors up to LGM nunataks, over a vertical range of some 2000 m; it is also present in catchments of the NCA that were not overridden by far-travelled ice streams and that lack metamorphic rock fragments. Two OSL quartz ages of the drape from two distinct locations (18.77 ± 1.55 ka; 17.81 ± 1.68 ka) fall into the early Alpine late-glacial interval shortly after the collapse of pleniglacial ice streams; this fits with geological and geomorphological evidence, respectively, that the drape should be of early late-glacial age, and that it accumulated during a specific interval of time. In the NCA, localized minor deposition of

Ground robotic measurement of aeolian processes

NASA Astrophysics Data System (ADS)

Qian, Feifei; Jerolmack, Douglas; Lancaster, Nicholas; Nikolich, George; Reverdy, Paul; Roberts, Sonia; Shipley, Thomas; Van Pelt, R. Scott; Zobeck, Ted M.; Koditschek, Daniel E.

2017-08-01

Models of aeolian processes rely on accurate measurements of the rates of sediment transport by wind, and careful evaluation of the environmental controls of these processes. Existing field approaches typically require intensive, event-based experiments involving dense arrays of instruments. These devices are often cumbersome and logistically difficult to set up and maintain, especially near steep or vegetated dune surfaces. Significant advances in instrumentation are needed to provide the datasets that are required to validate and improve mechanistic models of aeolian sediment transport. Recent advances in robotics show great promise for assisting and amplifying scientists' efforts to increase the spatial and temporal resolution of many environmental measurements governing sediment transport. The emergence of cheap, agile, human-scale robotic platforms endowed with increasingly sophisticated sensor and motor suites opens up the prospect of deploying programmable, reactive sensor payloads across complex terrain in the service of aeolian science. This paper surveys the need and assesses the opportunities and challenges for amassing novel, highly resolved spatiotemporal datasets for aeolian research using partially-automated ground mobility. We review the limitations of existing measurement approaches for aeolian processes, and discuss how they may be transformed by ground-based robotic platforms, using examples from our initial field experiments. We then review how the need to traverse challenging aeolian terrains and simultaneously make high-resolution measurements of critical variables requires enhanced robotic capability. Finally, we conclude with a look to the future, in which robotic platforms may operate with increasing autonomy in harsh conditions. Besides expanding the completeness of terrestrial datasets, bringing ground-based robots to the aeolian research community may lead to unexpected discoveries that generate new hypotheses to expand the science

Constraints on aeolian sediment transport to foredunes within an undeveloped backshore enclave on a developed coast

NASA Astrophysics Data System (ADS)

Kaplan, Kayla L.; Nordstrom, Karl F.; Jackson, Nancy L.

2016-10-01

Landforms present in undeveloped beach enclaves located between properties developed with houses and infrastructure are often left to evolve naturally but are influenced by the human structures near them. This field study evaluates how buildings and sand-trapping fences change the direction of wind approach, reduce wind speed, and restrict fetch distances for sediment entrainment, thereby reducing the potential for aeolian transport and development of dunes in enclaves. Field data were gathered in an 80 m long, 44 m deep beach enclave on the ocean shoreline of New Jersey, USA. Comparison of wind characteristics in the enclave with a site unaffected by buildings revealed that offshore winds in the enclave are reduced in strength and altered in direction by landward houses, increasing the relative importance of longshore winds. Vertical arrays of anemometers on the foredune crest, foredune toe and berm crest in the enclave revealed increasing wind speed with distance offshore, with strongest winds on the berm crest. Vertical cylindrical traps on the foredune crest, foredune toe, mid-backshore, berm crest and upper foreshore revealed the greatest rate of sediment transport on the berm crest. Sediment samples from the beach and from traps revealed limited potential for aeolian transport because of coarse grain sizes. Strong oblique onshore winds are common in this region and are normally important for transporting sand to dunes. The length of an enclave and the setback distance on its landward side determine the degree to which sediment delivered by oblique winds contributes to dune growth. The landward edge of the enclave (defined by a sand fence near the dune toe) is sheltered along its entire length from winds blowing at an angle to the shoreline of 25° or less. A foredune set back this distance in an enclave the length of an individual lot (about 20 m) would be sheltered at an angle of 57° or less, reducing the opportunity for dune building by onshore winds

Hydrodynamic implications of textural trends in sand deposits of the 2004 tsunami in Sri Lanka

USGS Publications Warehouse

Morton, R.A.; Goff, J.R.; Nichol, S.L.

2008-01-01

Field observations and sediment samples at a coastal-plain setting in southeastern Sri Lanka were used to document the erosional and depositional impacts of the 2004 Indian Ocean tsunami and to interpret the hydrodynamic processes that produced an extensive sand-sheet deposit. Tsunami deposit thicknesses ranged from 6 to 22??cm with thickness being controlled partly by antecedent topography. The deposit was composed of coarse to medium sand organized into plane-parallel laminae and a few laminasets. Vertical textural trends showed an overall but non-systematic upward fining and upward thinning of depositional units with an upward increase in heavy-mineral laminations at some locations. Repeated patterns in the vertical textural trends (upward fining, upward coarsening, uniform) were used to subdivide and correlate the deposit into five hydro-textural stratigraphic units. The depositional units were linked to hydrodynamic processes and upcurrent conditions, such as rates of sediment supply and composition of the sediment sources. Vertical changes in grain-size distributions recorded the depositional phases associated with flow acceleration, initial unsteady pulsating flow, relatively stable and uniform flow, flow deceleration, slack water, and return flow or flow redirection. Study results suggest that vertical textural trends from multiple cross-shore sections can be used to interpret complex tsunami flow histories, but at the location examined, interpretation of the lateral textural trends did not provide a basis for identifying the correct sediment transport pathways because flow near the landward boundary was multidirectional.

A new depositional model for sand-rich loess on the Buckley Flats outwash plain, northwestern Lower Michigan

NASA Astrophysics Data System (ADS)

Nyland, Kelsey E.; Schaetzl, Randall J.; Ignatov, Anthony; Miller, Bradley A.

2018-04-01

Loess was first studied in Michigan on the Buckley Flats, where outwash, overlain by ≈70 cm of loamy sediment, was originally interpreted as loess mixed with underlying sands. This paper re-evaluates this landscape through a spatial analysis of data from auger samples and soil pits. To better estimate the loamy sediment's initial textures, we utilized "filtered" laser diffraction data, which remove much of the coarser sand data. Textures of filtered silt data for the loamy sediment are similar to loess. The siltiest soils are found in the low-relief, central part of the Flats. Spatial analyses revealed that many silt fractions are nearly uniformly distributed, suggesting that the loess was not derived from a single source. The previous depositional model for the loamy mantle relied on loessfall followed by pedoturbation, but does not explain (1) the variation in sand contents across the Flats, or (2) the abrupt contact below the loamy mantle. This contact suggests that the outwash was frozen when the sediments above were deposited. Deep gullies at the western margins of the Flats were likely cut as permafrost facilitated runoff. Our new model for the origin of the loamy mantle suggests that the sands on the uplands were generated from eroding gullies and saltated onto the uplands along with loess that fell more widely. Sands saltating to the west of the Flats may have entrained some silts, facilitating loessfall downwind. At most sites, the loamy mantle gets increasingly silty near the surface, suggesting that saltation ended before loess deposition.

Monitoring of aeolian desertification on the Qinghai-Tibet Plateau from the 1970s to 2015 using Landsat images.

PubMed

Zhang, Chun-Lai; Li, Qing; Shen, Ya-Ping; Zhou, Na; Wang, Xue-Song; Li, Jiao; Jia, Wen-Ru

2018-04-01

Aeolian desertification, one of the most serious environmental issues, has hampered socioeconomic development on the Qinghai-Tibet Plateau (QTP). However, research on aeolian desertification in this region has been limited. To develop a set of science-based preventive measures to mitigate desertification in this region, it is first necessary to clarify the status, evolution, and driving factors of aeolian desertification. In this study, based on extensive field investigations and a current classification system for aeolian desertification, we established a new system for interpreting aeolian desertified land (ADL) on the plateau using Landsat images from 1977, 1990, 2000, 2010, and 2015 and obtained the distribution of ADL through visual interpretation of the images. The results showed that ADL covered 392,914km 2 (15.1% of the study area) in 2015, including gravel ADL, sandy ADL, and aeolian monadnocks. Controlled by climate, landforms, the type of Quaternary deposit, and human activities, ADL is scattered throughout the plateau but is concentrated mostly in the western and northern parts. Aeolian desertification on the plateau expanded from 1977 to 2000 and then began to reverse. The evolution during the study period is the result of the combined effects of natural and human factors. Irrational human activities were the dominant factor responsible for the expansion of ADL prior to 2000, whereas the subsequent reversal was mainly caused by climate change combined with large ecological restoration projects. Copyright © 2017 Elsevier B.V. All rights reserved.

On the frequency response of a Wenglor particle-counting system for aeolian transport measurements

NASA Astrophysics Data System (ADS)

Bauer, Bernard O.; Davidson-Arnott, Robin G. D.; Hilton, Michael J.; Fraser, Douglas

2018-06-01

A commonly deployed particle-counting system for aeolian saltation flux, consisting of a Wenglor fork sensor and an Onset Hobo Pulse Input Adapter linked to an Onset Hobo Energy Logger Pro data logger, was tested for frequency response. The Wenglor fork sensor is an optical gate device that has very fast switching capacity that can accommodate the time of flight of saltating sand particles through the sensing volume with the exception of very fine sand or silt and very quickly moving particles. The Pulse Input Adapter, in contrast, imposes limitations on the frequency response of the system. The manufacturer of the pulse adapter specifies an upper limit of 120 Hz, although bench tests with an electronic pulse generator indicate that the frequency response of the Pulse Input Adapter, in isolation, is excellent up to 3000 Hz, with only small error (less than 1.6%) due to under-counting during data transfer intervals. A mechanical test of the integrated system (fork sensor, pulse input adapter, and data logger) demonstrates excellent performance up to about 700 Hz (less than 2% error), but significant under-counting above 1000 Hz for unknown reasons. This specific particle-counting system therefore has a frequency response that is well suited for investigation of the dynamics of aeolian saltation as typically encountered in most field conditions on coastal beaches with the exception of extreme wind events and very small particle sizes.

Ancient wet aeolian environments on Earth: Clues to presence of fossil/live microorganisms on Mars

USGS Publications Warehouse

Mahaney, W.C.; Milner, M.W.; Netoff, D.I.; Malloch, D.; Dohm, J.M.; Baker, V.R.; Miyamoto, H.; Hare, T.M.; Komatsu, G.

2004-01-01

Ancient wet aeolian (wet-sabkha) environments on Earth, represented in the Entrada and Navajo sandstones of Utah, contain pipe structures considered to be the product of gas/water release under pressure. The sediments originally had considerable porosity allowing the ingress of living plant structures, microorganisms, clay minerals, and fine-grained primary minerals of silt and sand size from the surface downward in the sedimentary column. Host rock material is of a similar size and porosity and presumably the downward migration of fine-grained material would have been possible prior to lithogenesis and final cementation. Recent field emission scanning electron microscopy (FESEM) and EDS (energy-dispersive spectrometry) examination of sands from fluidized pipes in the Early Jurassic Navajo Sandstone reveal the presence of fossil forms resembling fungal filaments, some bearing hyphopodium-like structures similar to those produced by modern tropical leaf parasites. The tropical origin of the fungi is consistent with the paleogeography of the sandstone, which was deposited in a tropical arid environment. These fossil fungi are silicized, with minor amounts of CaCO3 and Fe, and in some cases a Si/Al ratio similar to smectite. They exist as pseudomorphs, totally depleted in nitrogen, adhering to the surfaces of fine-grained sands, principally quartz and orthoclase. Similar wet aeolian paleoenvironments are suspected for Mars, especially following catastrophic sediment-charged floods of enormous magnitudes that are believed to have contributed to rapid formation of large water bodies in the northern plains, ranging from lakes to oceans. These events are suspected to have contributed to a high frequency of constructional landforms (also known as pseudocraters) related to trapped volatiles and water-enriched sediment underneath a thick blanket of materials that were subsequently released to the martian surface, forming piping structures at the near surface and

Ancient wet aeolian environments on Earth: clues to presence of fossil/live microorganisms on Mars

NASA Astrophysics Data System (ADS)

Mahaney, William C.; Milner, Michael W.; Netoff, D. I.; Malloch, David; Dohm, James M.; Baker, Victor R.; Miyamoto, Hideaki; Hare, Trent M.; Komatsu, Goro

2004-09-01

Ancient wet aeolian (wet-sabkha) environments on Earth, represented in the Entrada and Navajo sandstones of Utah, contain pipe structures considered to be the product of gas/water release under pressure. The sediments originally had considerable porosity allowing the ingress of living plant structures, microorganisms, clay minerals, and fine-grained primary minerals of silt and sand size from the surface downward in the sedimentary column. Host rock material is of a similar size and porosity and presumably the downward migration of fine-grained material would have been possible prior to lithogenesis and final cementation. Recent field emission scanning electron microscopy (FESEM) and EDS (energy-dispersive spectrometry) examination of sands from fluidized pipes in the Early Jurassic Navajo Sandstone reveal the presence of fossil forms resembling fungal filaments, some bearing hyphopodium-like structures similar to those produced by modern tropical leaf parasites. The tropical origin of the fungi is consistent with the paleogeography of the sandstone, which was deposited in a tropical arid environment. These fossil fungi are silicized, with minor amounts of CaCO 3 and Fe, and in some cases a Si/Al ratio similar to smectite. They exist as pseudomorphs, totally depleted in nitrogen, adhering to the surfaces of fine-grained sands, principally quartz and orthoclase. Similar wet aeolian paleoenvironments are suspected for Mars, especially following catastrophic sediment-charged floods of enormous magnitudes that are believed to have contributed to rapid formation of large water bodies in the northern plains, ranging from lakes to oceans. These events are suspected to have contributed to a high frequency of constructional landforms (also known as pseudocraters) related to trapped volatiles and water-enriched sediment underneath a thick blanket of materials that were subsequently released to the martian surface, forming piping structures at the near surface and

Compositional trends in aeolian dust along a transect across the southwestern United States

USGS Publications Warehouse

Goldstein, H.L.; Reynolds, R.L.; Reheis, M.C.; Yount, J.C.; Neff, J.C.

2008-01-01

Aeolian dust strongly influences ecology and landscape geochemistry over large areas that span several desert ecosystems of the southwestern United States. This study evaluates spatial and temporal variations and trends of the physical and chemical properties of dust in the southwestern United States by examining dust deposited in natural depressions on high isolated surfaces along a transect from the Mojave Desert to the central Colorado Plateau. Aeolian dust is recognized in these depressions on the basis of textural, chemical, isotopic, and mineralogical characteristics and comparisons of those characteristics to the underlying bedrock units. Spatial and temporal trends suggest that although local dust sources are important to the accumulated material in these depressions, Mojave Desert dust sources may also contribute. Depth trends in the depressions suggest that Mojave sources may have contributed more dust to the Colorado Plateau recently than in the past. These interpretations point to the important roles of far-traveled aeolian dust for landscape geochemistry and imply future changes to soil geochemistry under changing conditions in far-distant dust source areas. Copyright 2008 by the American Geophysical Union.

Adhesion and abrasion of surface materials in the Venusian aeolian environment

NASA Technical Reports Server (NTRS)

Marshall, John R.; Greeley, Ronald; Tucker, David; Fogleman, Guy; Hixon, Raymond

1991-01-01

In laboratory simulations of the Venusian environment, rock and mineral 'target' surfaces struck by aeolian particles develop a thin layer of accretionary material derived from the particles' attrition debris. Accretion may be (in part) a manifestation of 'cold welding', a process well known in engineering, where bonding occurs between metals at a tribological interface. Accretion on geological materials was found to occur at all Venusian surface temperatures and for all types of materials tested. First-order variations in the amount deposited by particles are related to relative attrition susceptibilities. Second-order variations relate to properties of the particle-target interface. Variations in accretion volume are apparently independent of mineral chemistry and are only weakly dependent on crystallography. The results suggest that accretion should be a fairly universal phenomenon in areas of Venus subject to aeolian activity.

Influence of aeolian activities on the distribution of microbial abundance in glacier ice

NASA Astrophysics Data System (ADS)

Chen, Y.; Li, X.-K.; Si, J.; Wu, G.-J.; Tian, L.-D.; Xiang, S.-R.

2014-10-01

Microorganisms are continuously blown onto the glacier snow, and thus the glacial depth profiles provide excellent archives of microbial communities and climatic and environmental changes. However, it is uncertain about how aeolian processes that cause climatic changes control the distribution of microorganisms in the glacier ice. In the present study, microbial density, stable isotopic ratios, 18O / 16O in the precipitation, and mineral particle concentrations along the glacial depth profiles were collected from ice cores from the Muztag Ata glacier and the Dunde ice cap. The ice core data showed that microbial abundance was often, but not always associated with high concentrations of particles. Results also revealed clear seasonal patterning with high microbial abundance occurring in both the cooling autumn and warming spring-summer seasons. Microbial comparisons among the neighbouring glaciers display a heterogeneous spatial pattern, with the highest microbial cell density in the glaciers lying adjacent to the central Asian deserts and lowest microbial density in the southwestern margin of the Tibetan Plateau. In conclusion, microbial data of the glaciers indicates the aeolian deposits of microorganisms in the glacier ice and that the spatial patterns of microorgansisms are related to differences in sources of microbial flux and intensity of aeolian activities in the current regions. The results strongly support our hypothesis of aeolian activities being the main agents controlling microbial load in the glacier ice.

Deposit model for heavy-mineral sands in coastal environments: Chapter L in Mineral deposit models for resource assessment

USGS Publications Warehouse

Van Gosen, Bradley S.; Fey, David L.; Shah, Anjana K.; Verplanck, Philip L.; Hoefen, Todd M.

2014-01-01

Regional exploration for deposits of heavy-mineral sands can utilize the analyses of stream sediment samples for Ti, Hf, the rare earth elements, Th, and U, and geophysical surveys, particularly radiometric (gamma-ray spectrometry for K, U, and Th) and magnetic methods. Geophysical anomalies may be small, and surveys are generally more successful when conducted close to sources of interest.

Vertical structure of aeolian turbulence in a boundary layer with sand transport

NASA Astrophysics Data System (ADS)

Lee, Zoe S.; Baas, Andreas C. W.

2016-04-01

originating from the top of the boundary layer, indicating a downwards direction of eddy motion. While directionality of turbulence cannot be definitively determined, our results indicate that the top-down turbulence model is a suitable explanation, further supported by the presence of 'incomplete' eddies which originate at higher elevations but fail to extend to the surface. This provides the first evidence in support of a top down turbulence model as observed in aeolian geomorphology, and we present preliminary findings on its relationship to sand transport activity. Lee, Z.S., Baas, A.C.W. (2016) Variable and conflicting shear stress estimates inside a boundary layer with sediment transport. Earth Surface Processes and Landforms; DOI: 10.1002/esp.3829

Retention in Treated Wastewater Affects Survival and Deposition of Staphylococcus aureus and Escherichia coli in Sand Columns

PubMed Central

Li, Jiuyi; Zhao, Xiaokang; Tian, Xiujun; Li, Jin; Sjollema, Jelmer

2015-01-01

The fate and transport of pathogenic bacteria from wastewater treatment facilities in the Earth's subsurface have attracted extensive concern over recent decades, while the impact of treated-wastewater chemistry on bacterial viability and transport behavior remains unclear. The influence of retention time in effluent from a full-scale municipal wastewater treatment plant on the survival and deposition of Staphylococcus aureus and Escherichia coli strains in sand columns was investigated in this paper. In comparison to the bacteria cultivated in nutrient-rich growth media, retention in treated wastewater significantly reduced the viability of all strains. Bacterial surface properties, e.g., zeta potential, hydrophobicity, and surface charges, varied dramatically in treated wastewater, though no universal trend was found for different strains. Retention in treated wastewater effluent resulted in changes in bacterial deposition in sand columns. Longer retention periods in treated wastewater decreased bacterial deposition rates for the strains evaluated and elevated the transport potential in sand columns. We suggest that the wastewater quality should be taken into account in estimating the fate of pathogenic bacteria discharged from wastewater treatment facilities and the risks they pose in the aquatic environment. PMID:25595758

Late Quaternary extraglacial cold-climate deposits in low and mid-altitude Tasmania and their climatic implications

NASA Astrophysics Data System (ADS)

McIntosh, P. D.; Eberhard, R.; Slee, A.; Moss, P.; Price, D. M.; Donaldson, P.; Doyle, R.; Martins, J.

2012-12-01

Many Tasmanian deposits previously described as 'periglacial' have been described in more detail, re-interpreted and dated. We suggest that 'periglacial' has little meaning when applied locally and the term 'relict cold-climate deposits' is more appropriate. In this paper we examine the origin and age of relict cold-climate slope deposits, fan alluvium and aeolian sediments in Tasmania, and infer the conditions under which they accumulated. Fan alluvium dating from the penultimate Glacial (OIS 6) and capped by a prominent palaeosol deduced to date to the Last Interglacial (OIS 5e) is present at Woodstock, south of Hobart. Many fan deposits formed before 40 ka or in a period c. 30-23 ka; only a few deposits date to the Last Glacial Maximum in Tasmania, which is defined as spanning the period 23.5-17.5 ka. Slope deposits indicate widespread instability down to present-day sea level throughout the Last Glacial, probably as a result of freeze-thaw in a sparsely vegetated landscape. Layered fine gravel and coarse sand colluvial deposits resembling grèzes litées, produced both by dry deposition and by the action of water, are locally common where jointed siltstone bedrock outcrops. These deposits occur from altitudes of 500 m to near sea level and also in caves and must have formed under sparse vegetation cover, probably by freeze-thaw in extremely dry conditions. They have been radiocarbon dated from 35 to 17.5 cal. ka. Relict dunes and sandsheets are widespread at the margin of the Bassian Plain that once provided a land bridge between Tasmania and the mainland. They are also found in western Tasmania and in areas of inland southern Tasmania that now support wet eucalypt forest and rainforest and receive mean annual rainfall > 1500 mm. In the south they have been dated > 87.5-19 ka and attest to a long period of semi-arid climate in an area extending well to the west and south of the present semiarid zone. We deduce that during most of the Last Glacial anticyclones

Aeolian geomorphology from the global perspective

NASA Technical Reports Server (NTRS)

Greeley, R.

1985-01-01

Any planet or satellite having a dynamic atmosphere and a solid surface has the potential for experiencing aeolian (wind) processes. A survey of the Solar System shows at least four planetary objects which potentially meet these criteria: Earth, Mars, Venus, and possibly Titan, the largest satellite of Saturn. While the basic process is the same among these four objects, the movement of particles by the atmosphere, the aeolian environment is drastically different. It ranges from the hot (730 K), dense atmosphere of Venus to the extremely cold desert (218 K) environment of Mars where the atmospheric surface pressure is only approximately 7.5 mb. In considering aeolian processes in the planetary perspective, all three terrestrial planets share some common areas of attention for research, especially in regard to wind erosion and dust storms. Relevant properties of planetary objects potentially subject to aeolian processes are given in tabular form.

Radar-aeolian roughness project

NASA Technical Reports Server (NTRS)

Greeley, Ronald; Dobrovolskis, A.; Gaddis, L.; Iversen, J. D.; Lancaster, N.; Leach, Rodman N.; Rasnussen, K.; Saunders, S.; Vanzyl, J.; Wall, S.

1991-01-01

The objective is to establish an empirical relationship between measurements of radar, aeolian, and surface roughness on a variety of natural surfaces and to understand the underlying physical causes. This relationship will form the basis for developing a predictive equation to derive aeolian roughness from radar backscatter. Results are given from investigations carried out in 1989 on the principal elements of the project, with separate sections on field studies, radar data analysis, laboratory simulations, and development of theory for planetary applications.

Grain-Scale Analyses of Curiosity Data at Marias Pass, Gale Crater, Mars: Methods Comparison and Depositional Interpretation

NASA Astrophysics Data System (ADS)

Sacks, L. E.; Edgar, L. A.; Edwards, C. S.; Anderson, R. B.

2016-12-01

Images acquired by the Mars Hand Lens Imager (MAHLI) and the ChemCam Remote Micro Imager (RMI) onboard the Mars Science Laboratory (MSL) Curiosity rover provide grain-scale data that are critical for interpreting sedimentary deposits. At the location informally known as Marias Pass, Curiosity used both cameras to image the nine rock targets used in this study. We used manual point-counts to measure grain size distributions from those images to compare the abilities of the two cameras. The manually derived results were compared to automated grain size data obtained using pyDGS (Digital Grain Size), an open-source python program. Grain size analyses were used to test the lacustrine and aeolian depositional hypotheses for the Murray and Stimson formations at Marias Pass. Results indicate that the MAHLI and RMI instruments, despite their different fields of view and properties, provide comparable grain size measurements. Additionally, pyDGS does not account for grains smaller than a few pixels and thus does not report representative grain size data and should not be used on images with a large fraction of unresolved grains. Finally, the data collected at Marias Pass are consistent with the existing interpretations of the Murray and Stimson formations. The fine-grained results of the Murray formation analyses support lacustrine deposition, while the mean grain size of the Stimson formation is fine to medium sized sand, consistent with aeolian deposition. However, directly above the contact with the Murray formation, larger rip-up clasts of the Murray formation are present in the Stimson formation. It is possible that water was involved at this stage of erosion and re-deposition, prior to aeolian deposition. Additionally, the grain-scale analyses conducted in this study show that the Dust Removal Tool on Curiosity should be used prior to capturing images for grain-scale analysis. Two images of the target informally named Ronan, taken before and after brushing, resulted

Origin and prospectivity of heavy mineral enriched sand deposits along the Somaliland coastal areas

NASA Astrophysics Data System (ADS)

Ali, M. Y.; Hibberd, P.; Stoikovich, B.

2018-04-01

Sixty-one heavy mineral enriched samples along the Somaliland coast from Eil Sheikh to Ras Khatib, a distance of about 130 km, were analyzed using X-ray Fluorescence, X-ray Diffraction and SEM-EDS techniques. This study reveals that a considerable amount of heavy minerals is present along the Somaliland coast and confirms the presence of high concentration titanium and iron bearing minerals. However, the backshore deposits in the mouths of Waaheen and Biyo Gure ephemeral rivers as well as raised paleo-beaches in the east of port city of Berbera demonstrate the highest level of titaniferous heavy minerals with most samples showing concentration greater than 50 wt %. The titanium detected in geochemical analysis occurs in the form of ilmenite, rutile, titanite and titaniferous magnetite. Also, present in minor or trace amounts, are garnet, zircon and monazite. Heavy mineral accumulations in the east and west of Berbera have different mineralogical assemblages. The east of Berbera is dominated by quartz with moderate concentration of plagioclase, K-feldspar, magnetite, hematite and titanium bearing minerals, whereas in the west of Berbera, the dominant minerals are quartz, K-feldspar and plagioclase with variable proportions of ilmenite, rutile, mica, amphibole and pyroxene. These variations in mineral assemblages suggest different composition of the catchment areas that supply sediment to these deposits. The catchment area in the east of Berbera consists mainly of Proterozoic crystalline basement of the Qabri Bahar complex, Gabbro-Synenite belt and granitic intrusions that outcrop in Hudiso, Tulo Dibijo and surrounding areas. The primary sources of heavy minerals in the west of Berbera comprise of high-grade metamorphic rocks of the Mora and Qabri Bahar complexes as well as the Miocene volcanics that outcrop in Laferug and Hagabo areas. The heavy mineral sand deposits observed along the Somaliland coast have the potential to provide commercially important heavy

Maps showing characteristics of the Cabo Rojo West offshore sand deposit, southwestern Puerto Rico

USGS Publications Warehouse

Trumbull, James V.A.; Trias, Juan L.

1982-01-01

This report presents detailed information on a deposit of well-sorted coarse calcareous sand in water depths of 10-20 m in an area between 1 and 6 km west and southwest fo the promontory of Cabo Rojo, the southwesternmost corner of Puerto Rico. 

Size-Selective Modes of Aeolian Transport on Earth and Mars

NASA Astrophysics Data System (ADS)

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

2016-12-01

Aeolian sand transport is a dominant driver of surface change and dust emission on Mars. Estimates of aeolian sand transport on Earth and Mars rely on terrestrial transport models that do not differentiate between transport modes (e.g., creep vs. saltation), which limits estimates of the critical threshold for transport and the total sand flux during a transport event. A gap remains in understanding how the different modes contribute to the total sand flux. Experiments conducted at the MARtian Surface WInd Tunnel separated modes of transport for uniform and mixed grain size surfaces at Earth and Martian atmospheric pressures. Crushed walnut shells with a density of 1.0 gm/cm3 were used. Experiments resolved grain size distributions for creeping and saltating grains over 3 uniform surfaces, U1, U2, and U3, with median grain sizes of 308 µm, 721 µm, and 1294 µm, and a mixed grain size surface, M1, with median grain sizes of 519 µm. A mesh trap located 5 cm above the test bed and a surface creep trap were deployed to capture particles moving as saltation and creep. Grains that entered the creep trap at angles ≥ 75° were categorized as moving in creep mode only. Only U1 and M1 surfaces captured enough surface creep at both Earth and Mars pressure for statistically significant grain size analysis. Our experiments show that size selective transport differs between Earth and Mars conditions. The median grain size of particles moving in creep for both uniform and mixed surfaces are larger under Earth conditions. (U1Earth = 385 µm vs. U1Mars = 355 µm; M1Earth = 762 vs. M1Mars = 697 µm ). However, particles moving in saltation were larger under Mars conditions (U1Earth = 282 µm; U1Mars = 309 µm; M1Earth = 347 µm; M1Mars = 454 µm ). Similar to terrestrial experiments, the median size of surface creep is larger than the median grain size of saltation. Median sizes of U1, U2, U3 at Mars conditions for creep was 355 µm, 774 µm and 1574 µm. Saltation at Mars

Aeolian Grain Evolution on Mars: Implications for Regolith Origins

NASA Astrophysics Data System (ADS)

Sullivan, R. J.; Cabrol, N. A.; Golombek, M.; Herkenhoff, K. E.; Landis, G.; Mer Athena Science Team

2010-12-01

Early wind tunnel experiments and the Viking Lander experience led to concepts of grain evolution and regolith development on Mars. Wind tunnel experiments showed that 100-150 μm grains are easiest to entrain on Mars, but at 10 times higher wind speeds than on Earth. Even if trajectory speeds of martian saltating grains achieve smaller fractions of entraining wind speeds than on Earth, kinetic energies of these grains would be much higher, with greater potential for damage to the grains during return collisions with the particle bed. On this basis Sagan et al. [1977] JGR 82, 28, 4430 proposed that aeolian grain evolution on Mars followed a “kamikaze” pattern in which an initially coarse grain, entrained only relatively rarely by the strongest winds, would be abraded by high kinetic energy impacts and migrate through successively smaller size-frequencies at an ever-increasing rate (as entrainment became easier and thus more likely) until the grain was essentially turned to dust. On this basis it was proposed that sand-sized grains might be relatively short-lived and perhaps rare on Mars. MER observations motivate adjustments to these concepts, with implications for origins of martian regolith reworked by wind. Along both MER traverses, on opposite sides of the planet, regolith is volumetrically dominated by very fine sand mixed with unresolved finer grains. Sorting probably is poor, based on weakly cohesive remolding by rover wheel cleats. The size-frequency of this material, even if not precisely known, is consistent with grains that have evolved by attrition to sizes smaller than the most easily-moved 100-150 μm interval, to where entrainment becomes more difficult due to the increasing relative importance of inter-particle surface forces. At these smaller sizes also, kinetic energies have been reduced proportionally by the cube of the particle radius, so grain-to-grain attrition is less effective for further evolution to even smaller grain sizes

Relating sedimentary processes in the Bagnold Dunes to the development of crater basin aeolian stratification

NASA Astrophysics Data System (ADS)

Ewing, R. C.; Lapotre, M. G. A.; Lewis, K. W.; Day, M. D.; Stein, N.; Rubin, D. M.; Sullivan, R. J., Jr.; Banham, S.; Thomas, N. M.; Lamb, M. P.; Gupta, S.; Fischer, W. W.

2017-12-01

Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under martian conditions. Exploration of the Bagnold Dunes by the Curiosity Rover in Gale Crater, Mars provided the first opportunity to make in situ observations of martian dunes from the grain-to-dune scale. We used the suite of cameras on Curiosity, including Navigation Camera, Mast Camera, and Mars Hand Lens Imager. We measured grainsize and identified sedimentary processes similar to processes on terrestrial dunes, such as grainfall, grainflow, and impact ripples. Impact ripple grainsize had a median of 0.103 mm. Measurements of grainflow slopes indicate a relaxation angle of 29° and grainfall slopes indicate critical angles of at least 32°. Dissimilar to terrestrial dunes, large, meter-scale ripples form on all slopes of the dunes. The ripples form both sinuous and linear crestlines, have symmetric and asymmetric profiles, range in height between 12cm and 28cm, and host grainfall, grainflow, and impact ripples. The largest ripples are interpreted to integrate the annual wind cycle within the crater, whereas smaller large ripples and impact ripples form or reorient to shorter term wind cycling. Assessment of sedimentary processes in combination with dune type across the Bagnold Dunes shows that dune-field pattern development in response to a complex crater-basin wind regime dictates the distribution of geomorphic processes. From a stratigraphic perspective, zones of highest potential accumulation correlate with zones of wind convergence, which produce complex winds and dune field patterns thereby

Research of wind erosion intensity in the region of Subotica-Horgos sands

Treesearch

Velizar Velasevic; Ljubomir Letic

1991-01-01

Wind is an important erosional process in the areas of steppe-savanna climate in Europe as typified by the Bojvodina plain in Yugoslavia. Cultivated and forested plots on the Subotica-Horgos Sands were used to study aeolian erosion processes. Wind erosion on the cultivated plot was 3-29 times greater than that occurring on a plot planted to forest trees. That erosion...

Discrimination of active and inactive sand from remote sensing - Kelso dunes, Mojave Desert, California

NASA Technical Reports Server (NTRS)

Paisley, Elizabeth C. I.; Lancaster, Nicholas; Gaddis, Lisa R.; Greeley, Ronald

1991-01-01

Landsat TM images, field data, and laboratoray reflectance spectra were examined for the Kelso dunes, Mojave Desert, California to assess the use of visible and near-infrared (VNIR) remote sensing data to discriminate aeolian sand populations on the basis of spectral brightness. Results show that areas of inactive sand have a larger percentage of dark, fine-grained materials compared to those composed of active sand, which contain less dark fines and a higher percentage of quartz sand-size grains. Both areas are spectrally distinct in the VNIR, suggesting that VNIR spectral data can be used to discriminate active and inactive sand populations in the Mojave Desert. Analysis of laboratory spectra was complicated by the presence of magnetite in the active sands, which decreases their laboratory reflectance values to those of inactive sands. For this application, comparison of TM and laboratory spectra suggests that less than 35 percent vegetation cover does not influence the TM spectra.

Effects of sand burial on dew deposition on moss soil crust in a revegetated area of the Tennger Desert, Northern China

NASA Astrophysics Data System (ADS)

Jia, Rong-liang; Li, Xin-rong; Liu, Li-chao; Pan, Yan-xia; Gao, Yan-hong; Wei, Yong-ping

2014-11-01

Sand burial and dew deposition are two fundamental phenomena profoundly influencing biological soil crusts in desert areas. However, little information is available regarding the effects of sand burial on dew deposition on biological soil crusts in desert ecosystems. In this study, we evaluated the effects of sand burial at depths of 0 (control), 0.5, 1, 2 and 4 mm on dew formation and evaporation of three dominant moss crusts in a revegetated area of the Tengger Desert (Northern China) in 2010. The results revealed that sand burial significantly decreased the amount of dew deposited on the three moss crust types by acting as a semi-insulator retarding the dew formation and evaporation rates. The changes in surface temperature cannot fully explain the variations of the formation and evaporation rates of dew by moss crusts buried by sand. The extension of dew retention time was reflected by the higher dew ratios (the ratio of dew amount at a certain time to the maximum value in a daily course) in the daytime, and may to some extent have acted as compensatory mechanisms that diminished the negative effects of the reduction of dew amount induced by sand burial of moss crusts. The resistances to reduction of dewfall caused by sand burial among the three moss crusts were also compared and it was found that Bryum argenteum crust showed the highest tolerance, followed by crusts dominated by Didymodon vinealis and Syntrichia caninervis. This sequence corresponds well with the successional order of the three moss crusts in the revegetated area, thereby suggesting that resistance to reduction of dewfall may act as one mechanism by which sand burial drives the succession of moss crusts in desert ecosystems. This side effect of dew reduction induced by sand burial on biological soil crusts should be considered in future ecosystem construction and management of desert area.

Quantification of annual sediment deposits for sustainable sand management in Aghanashini river estuary.

PubMed

Ramachandra, T V; Vinay, S; Subash Chandran, M D

2018-01-15

Sedimentation involving the process of silt transport also carries nutrients from upstream to downstream of a river/stream. Sand being one of the important fraction of these sediments is extracted in order to cater infrastructural/housing needs in the region. This communication is based on field research in the Aghanshini river basin, west coast of India. Silt yield in the river basin and the sedimentation rate assessed using empirical techniques supplemented with field quantifications using soundings (SONAR), show the sediment yield of 1105-1367 kilo cum per year and deposition of sediment of 61 (2016) to 71 (2015) cm. Quantifications of extractions at five locations, reveal of over exploitation of sand to an extent of 30% with damages to the breeding ground of fishes, reduced productivity of bivalves, etc., which has affected dependent people's livelihood. This study provides vital insights towards sustainable sand harvesting through stringent management practices. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sulfur-Bearing Phases Detected by Evolved Gas Analysis of the Rocknest Aeolian Deposit, Gale Crater, Mars

NASA Technical Reports Server (NTRS)

Mcadam, Amy Catherine; Franz, Heather Bryant

2014-01-01

The Sample Analysis at Mars (SAM) instrument suite detected SO2, H2S, OCS, and CS2 from approx.450 to 800 C during evolved gas analysis (EGA) of materials from the Rocknest aeolian deposit in Gale Crater, Mars. This was the first detection of evolved sulfur species from a Martian surface sample during in situ EGA. SO2(approx. 3-22 micro-mol) is consistent with the thermal decomposition of Fe sulfates or Ca sulfites, or evolution/desorption from sulfur-bearing amorphous phases. Reactions between reduced sulfur phases such as sulfides and evolved O2 or H2O in the SAM oven are another candidate SO2 source. H2S (approx.41-109 nmol) is consistent with interactions of H2O, H2 and/or HCl with reduced sulfur phases and/or SO2 in the SAM oven. OCS (approx.1-5 nmol) and CS2(approx.0.2-1 nmol) are likely derived from reactions between carbon-bearing compounds and reduced sulfur. Sulfates and sulfites indicate some aqueous interactions, although not necessarily at the Rocknest site; Fe sulfates imply interaction with acid solutions whereas Ca sulfites can form from acidic to near-neutral solutions. Sulfides in the Rocknest materials suggest input from materials originally deposited in a reducing environment or from detrital sulfides from an igneous source. The presence of sulfides also suggests that the materials have not been extensively altered by oxidative aqueous weathering. The possibility of both reduced and oxidized sulfur compounds in the deposit indicates a nonequilibrium assemblage. Understanding the sulfur mineralogy in Rocknest materials, which exhibit chemical similarities to basaltic fines analyzed elsewhere on Mars, can provide insight in to the origin and alteration history of Martian surface materials.

Retrogressive Failures in Sand Deposits of the Mississippi River. Report 1. Field Investigations, Laboratory Studies and Analysis of the Hypothesized Failure Mechanism

DTIC Science & Technology

1988-06-01

densities of Mississippi River point bar sands . 73. It is particularly conclusive to compare the available critical void ratio data for point bar sands on... River encounters the difficulty that the density of large parts of Zone A sands is between the upper and lower critical densities . All laboratory... sands of the Lower Mississippi River point bar deposits generally contain some strata of subcritical density , and the initial tendenc% of such sands

Cenozoic record of aeolian sediment accumulation and aridification from Lanzhou, China, driven by Tibetan Plateau uplift and global climate

NASA Astrophysics Data System (ADS)

Zhang, Yuebao; Sun, Donghuai; Li, Zaijun; Wang, Fei; Wang, Xin; Li, Baofeng; Guo, Feng; Wu, Sheng

2014-09-01

Previous work has shown that aeolian Red Clay first appears at around 8 Ma in the main Chinese Loess Plateau and at 25-22 Ma in the western Loess Plateau; however, records of aeolian deposition in the North Pacific suggest that aeolian accumulation occurred throughout the Cenozoic, and that changes in aeolian flux occurred in distinct stages. Tracing the Cenozoic aeolian history of the interior of the Asian continent may help us to understand the history of Asian aridification and its driving forces. In the Lanzhou area on the western margin of the Loess Plateau and the northeastern edge of the Tibetan Plateau, the Cenozoic stratigraphic sequence consists of fluvial-lacustrine sediments in the lower part, aeolian Red Clay with intercalated fluvial layers in the middle part, and predominantly aeolian loess in the upper part. We use high resolution paleomagnetic measurements of this sequence to construct a time scale, and measurements of sediment rock magnetic properties, grain-size, and color reflectance and sedimentary facies analysis to reconstruct the paleoenvironment. The results show that prior to 33 Ma the area was dominantly a fluvial-lacustrine environment, and that subsequently an aridification trend commenced, as indicated by the appearance of aeolian sediment. This change coincided with, and is thus explained as the environmental response to global cooling. A significant increase in aeolian sediments occurred at ~ 26 Ma, suggesting that a large scale arid environment had formed in the Asian interior since the late Oligocene. Stepwise increases of aeolian sediment, and decreases in sediments of hydraulic origin, occurred at ~ 22, ~ 14, ~ 8 and 2.6 Ma and represent important stages in the aridification process. This long-term trend was interrupted by intervals dominated by fluvial sedimentation at 23.6-22 Ma and 17.1-14.1 Ma and which were probably associated with warming of the global climate and the tectonic uplift of the northeastern Tibetan Plateau

Coupling Aeolian Stratigraphic Architecture to Paleo-Boundary Conditions: The Scour-Fill Dominated Jurassic Page Sandstone

NASA Astrophysics Data System (ADS)

Cardenas, B. T.; Kocurek, G.; Mohrig, D. C.; Swanson, T.

2017-12-01

The stratigraphic architecture of aeolian sandstones is thought to encode signals originating from both autogenic dune behavior and allogenic boundary conditions within which the dune field evolves. Mapping of outcrop-scale bounding surfaces and sets of cross-strata between these surfaces for the Jurassic Page Sandstone near Page, AZ, USA, demonstrates that dune autogenic behavior manifested in variable dune scour depth, whereas the dominant boundary conditions were antecedent topography and water-table elevation. At the study area, the Page Sandstone is 60 m thick and is separated from the underlying Navajo Sandstone by the J-2 regional unconformity, which shows meters of relief. Filling J-2 depressions are thin, climbing sets of cross-strata. In contrast, the overlying Page consists of packages of one to a few, meter-scale sets of cross-strata between the outcrop-scale bounding surfaces. These surfaces, marked by polygonal fractures and local overlying sabkha deposits, are regional in scale and correlated to high stands of the adjacent Carmel sea. Over the km-scale outcrop, the surfaces show erosional relief and packages of cross-strata are locally truncated. Notably absent within these cross-strata packages are early dune-field accumulations, interdune deposits, and apparent dune-climbing. These strata are interpreted to represent a scour-fill architecture created by migrating large dunes within a mature dry aeolian sand sea, in which early phases of dune-field construction have been cannibalized and dune fill of the deepest scours is recorded. At low angles of climb, set thickness is dominated by the component of scour-depth variation over the component resulting from the angle of climb. After filling of J-2 depressions, the Page consists of scour-fill accumulations formed during low stands. Carmel transgressions limited sediment availability, causing deflation to the water table and development of the regional bounding surfaces. Each subsequent fall of the

Surface-Based 3d measurements of aeolian bedforms on Mars

NASA Astrophysics Data System (ADS)

Balme, Matthew; Robson, Ellen; Barnes, Robert; Huber, Ben; Butcher, Frances; Fawdon, Peter; Gupta, Sanjeev; Paar, Gerhard

2017-04-01

The surface of Mars hosts many different types of aeolian bedforms, from small wind-ripples with cm-scale wavelength, through decametre-scale "Transverse Aeolian Ridges" (TARs), to km-scale dunes. To date, all mobile Mars surface-missions ('Rovers') have encountered aeolian bedforms of one kind or another. Aeolian deposits of loose, unconsolidated material provide hazards to Mars Rovers: sinkage into the aeolian material and enhanced slippage can prevent traction and forward progress, forcing the Rover to backtrack (e.g., MER Opportunity) and can even 'trap' the rover ending the mission (e.g., MER Spirit). Here, we present morphometry measurements of meter-scale ripple-like bedforms on Mars, as observed by the MER Opportunity Rover during its traverse across the Meridiani Planum region of Mars. The aim is to assess whether there is a relationship between bedforms parameters that can be measured from orbit such as length and width, and bedform height, which can only be reliably measured from orbit for larger features such as TARs. If such a relationship can be found, it might allow estimates of ripple-height to be made from remote sensing data alone. This could help understand the formation mechanism and provide a better characterization of the hazard presented by these features. For much of the first 30 km of the traverse, Opportunity travelled across flat plains with meter-scale, ripple-like aeolian bedforms ("plains ripples") superposed upon them. During the traverse, the Rover acquired stereo imaging data of its surroundings using both its scientific Pancam cameras system and the navigational Navcam system. Using these data, and newly developed Pro3D™ and PRoViP™ software from Joanneum Research, we obtained Digital Elevation Models of many areas along the traverse, allowing us to measure the heights, widths and lengths of aeolian bedforms. In addition, the same bedforms were digitized from orbital HiRISE image data (25 cm/pix resolution) in ArcGIS software

[Spatial change of the grain-size of aeolian sediments in Qira oasis-desert ecotone, Northwest China].

PubMed

Lin, Yong Chong; Xu, Li Shuai

2017-04-18

In order to understand the environmental influence of oasis-desert ecotone to oasis ecological system, we comparatively analyzed the grain size characteristics of various aeolian sediments, including the sediments in oasis-desert ecotone, shelterbelt and the inside oasis and in Qira River valley. The results showed that the grain size characteristics (including grain-size distribution curve, grain size parameters, and content of different size classes) of sediments in the oasis-desert ecotone were consistent along the prevailing wind direction with a grain-size range of 0.3-200 μm and modal size of 67 μm. All of the sediments were good sorting and mainly composed of suspension components and saltation components, but not denatured saltation and creeping components (>200 μm). They were typically aeolian deposits being short-range transported. The grain sizes of sediments in oasis-desert ecotone were smaller than that in the material sources of Qira River valley and desert (0.3-800 μm), but very similar to those of the modern aeolian deposits in oasis-desert ecotone, shelterbelt and the inside oasis. The denatured saltation and creep components (>200 μm) were suppressed to transport into oasis-desert ecotone because of the high vegetation cover in oasis-desert ecotone. Therefore, like the shelterbelts, the oasis-desert ecotone could also block the invasion of desert. They safeguarded the oasis ecological environment together.

Deposition of Suspended Clay to Open and Sand-Filled Framework Gravel Beds in a Laboratory Flume

NASA Astrophysics Data System (ADS)

Mooneyham, Christian; Strom, Kyle

2018-01-01

Pulses of fine sediment composed of sand, silt, and clay can be introduced to gravel bed rivers through runoff from burn-impacted hillslopes, landslides, bank failure, or the introduction of reservoir sediment as a result of sluicing or dam decommissioning. Here we present a study aimed at quantifying exchange between suspensions of clay and gravel beds. The questions that motivate the work are: how do bed roughness and pore space characteristics, shear velocity (u∗), and initial concentration (C0) affect clay deposition on or within gravel beds? Where does deposition within these beds occur, and can deposited clay be resuspended while the gravel is immobile? We examine these questions in a laboratory flume using acrylic, open-framework gravel, and armored sand-gravel beds under conditions of varying u∗ and C0. Deposition of clay occurred to all beds (even with Rouse numbers ˜ 0.01). We attribute deposition under full suspension conditions to be an outcome of localized protected zones where clay can settle and available pore space in the bed. For smooth wall cases, protection came from the viscous wall region and the development of bed forms; for the rough beds, protection came from separation zones and low-velocity pore spaces. Bed porosity was the strongest influencer of nondimensional deposition rate; deposition increased with porosity. Deposition was inversely related to u∗ for the acrylic bed runs; no influence of u∗ was found for the porous bed runs. Increases in discharge resulted in resuspension of clay from acrylic beds; no resuspension was observed in the porous bed runs.

Tracing industrial sulfur emissions in atmospheric sulfate deposition in the Athabasca Oil Sands Region, Alberta, Canada

Treesearch

Bernadette C. Proemse; Bernhard Mayer; Mark E. Fenn

2012-01-01

Anthropogenic S emissions in the Athabasca oil sands region (AOSR) in Alberta, Canada, affect SO4 deposition in close vicinity of industrial emitters. Between May 2008 and May 2009, SO4-S deposition was monitored using open field bulk collectors at 15 sites and throughfall collectors at 14 sites at distances between 3 and 113 km from one of the major emission stacks in...

Identification of source locations for atmospheric dry deposition of heavy metals during yellow-sand events in Seoul, Korea in 1998 using hybrid receptor models

NASA Astrophysics Data System (ADS)

Han, Young-Ji; Holsen, Thomas M.; Hopke, Philip K.; Cheong, Jang-Pyo; Kim, Ho; Yi, Seung-Muk

2004-10-01

Elemental dry deposition fluxes were measured using dry deposition plates from March to June 1998 in Seoul, Korea. During this spring sampling period several yellow-sand events characterized by long-range transport from China and Mongolia impacted the area. Understanding the impact of yellow-sand events on atmospheric dry deposition is critical to managing the heavy metal levels in the environment in Korea. In this study, the measured flux of a primarily crustal metal, Al and an anthropogenic metal, Pb was used with two hybrid receptor models, potential source contribution function (PSCF) and residence time weighted concentration (RTWC) for locating sources of heavy metals associated with atmospheric dry deposition fluxes during the yellow-sand events in Seoul, Korea. The PSCF using a criterion value of the 75th percentile of the measured dry deposition fluxes and RTWC results using the measured elemental dry deposition fluxes agreed well and consistently showed that there were large potential source areas in the Gobi Desert in China and Mongolia and industrial areas near Tianjin, Tangshan, and Shenyang in China. Major industrial areas of Shenyang, Fushun, and Anshan, the Central China loess plateau, the Gobi Desert, and the Alashan semi-desert in China were identified to be major source areas for the measured Pb flux in Seoul, Korea. For Al, the main industrial areas of Tangshan, Tianjin and Beijing, the Gobi Desert, the Alashan semi-desert, and the Central China loess plateau were found to be the major source areas. These results indicate that both anthropogenic sources such as industrial areas and natural sources such as deserts contribute to the high dry deposition fluxes of both Pb and Al in Seoul, Korea during yellow-sand events. RTWC resolved several high potential source areas. Modeling results indicated that the long-range transport of Al and Pb from China during yellow-sand events as well as non-yellow-sand spring daytimes increased atmospheric dry

Differential Effects of High Atmospheric N and S Deposition on Bog Plant/Lichen Tissue and Porewater Chemistry across the Athabasca Oil Sands Region.

PubMed

Wieder, R Kelman; Vile, Melanie A; Scott, Kimberli D; Albright, Cara M; McMillen, Kelly J; Vitt, Dale H; Fenn, Mark E

2016-12-06

Oil extraction and development activities in the Athabasca Oil Sands Region of northern Alberta, Canada, release NO x , SO x , and NH y to the atmosphere, ultimately resulting in increasing N and S inputs to surrounding ecosystems through atmospheric deposition. Peatlands are a major feature of the northern Alberta landscape, with bogs covering 6-10% of the land area, and fens covering 21-53%. Bulk deposition of NH 4 + -N, NO 3 - -N, dissolved inorganic N (DIN), and SO 4 2- -S, was quantified using ion-exchange resin collectors deployed at 23 locations, over 1-6 years. The results reveal maximum N and S deposition of 9.3 and 12.0 kg ha -1 yr -1 , respectively, near the oil sands industrial center (the midpoint between the Syncrude and Suncor upgrader stacks), decreasing with distance to a background deposition of 0.9 and 1.1 kg ha -1 yr -1 , respectively. To assess potential influences of high N and S deposition on bogs, we quantified N and S concentrations in tissues of two Sphagnum species, two lichen species, and four vascular plant species, as well as surface porewater concentrations of H + , NH 4 + -N, NO 3 - -N, SO 4 2- -S and dissolved organic N in 19 ombrotrophic bogs, distributed across a 3255 km 2 sampling area surrounding the oil sands industrial center. The two lichen species (Evernia mesomorpha and Cladonia mitis), two vascular plant species (Rhododendron groenlandicum and Picea mariana), and to a lesser extent one moss (Sphagnum fuscum), showed patterns of tissue N and S concentrations that were (1) highest near the oil sands industrial center and (2) positively correlated with bulk deposition of N or S. Concentrations of porewater H + and SO 4 2- -S, but not of NH 4 + -N, NO 3 - -N, DIN, or dissolved inorganic N, also were higher near the oil sands industrial center than at more distant locations. The oil sands region of northern Alberta is remote, with few roads, posing challenges to the monitoring of oil sands-related N and S deposition

Spatial and temporal patterns of airflow across a foredune and beach surface under offshore winds: implications for aeolian sediment transport

NASA Astrophysics Data System (ADS)

Jackson, D.; Delgado-Fernandez, I.; Lynch, K.; Baas, A. C.; Cooper, J. A.; Beyers, M.

2010-12-01

The input of aeolian sediment into foredune systems from beaches represents a key component of sediment budget analysis along many soft sedimentary coastlines. Where there are significant offshore wind components in local wind regimes this is normally excluded from analysis. However, recent work has shown that if the topography of the foredune is favourable then this offshore component is steered or undergoes flow reversal through leeside eddying to give onshore transport events at the back beach under offshore flow conditions. At particular distances from the foredune crest flow reattaches to the surface to continue its incident offshore direction. The location of this reattachment point has important implications for aeolian transport of sand on the back beach and foredune toe locations. This study reports initial results where the positioning of the reattachment point is mobile and is driven by incident wind velocity (at the foredune crest) and the actual undulations of the foredune crest’s topography, dictating heterogeneous flow behaviour at the beach. Using detailed field measurements (25 Hz, three-dimensional sonic anemometry) and computational fluid dynamic modelling, a temporal and spatial pattern of reattachment positions are described. Implications for aeolian transport and dune evolution are also examined.

Abstracts for the Planetary Geology Field Conference on Aeolian Processes

NASA Technical Reports Server (NTRS)

Greeley, R. (Editor); Black, D. (Editor)

1978-01-01

The Planetary Geology Field Conference on Aeolian Processes was organized at the request of the Planetary Geology Program office of the National Aeronautics and Space Administration to bring together geologists working on aeolian problems on earth and planetologists concerned with similar problems on the planets. Abstracts of papers presented at the conference are arranged herein by alphabetical order of the senior author. Papers fall into three broad categories: (1) Viking Orbiter and Viking Lander results on aeolian processes and/or landforms on Mars, (2) laboratory results on studies of aeolian processes, and (3) photogeology and field studies of aeolian processes on Earth.

Turbulent flow structures and aeolian sediment transport over a barchan sand dune

NASA Astrophysics Data System (ADS)

Wiggs, G. F. S.; Weaver, C. M.

2012-03-01

The turbulent structure of airflow over a barchan sand dune is determined using quadrant analysis of wind velocity data derived from sonic anemometers. Results indicate an increased frequency of ejection and sweep events in the toe region of the dune, characteristic of the turbulent bursting process. In contrast, at the crest there was a significant increase in the occurrence of outward interactions. Combined with high frequency saltation data our analyses show that turbulent structures characterised by a positive streamwise fluctuating velocity (+u‧ sweeps at the toe and outward interactions at the crest) have a dominant influence on sand transport on the dune, together accounting for up to 83% and 95% of transporting events at the toe and crest respectively.

Spatial variation in deposition rate coefficients of an adhesion-deficient bacterial strain in quartz sand.

PubMed

Tong, Meiping; Camesano, Terri A; Johnson, William P

2005-05-15

The transport of bacterial strain DA001 was examined in packed quartz sand under a variety of environmentally relevant ionic strength and flow conditions. Under all conditions, the retained bacterial concentrations decreased with distance from the column inlet at a rate that was faster than loglinear, indicating that the deposition rate coefficient decreased with increasing transport distance. The hyperexponential retained profile contrasted againstthe nonmonotonic retained profiles that had been previously observed for this same bacterial strain in glass bead porous media, demonstrating that the form of deviation from log-linear behavior is highly sensitive to system conditions. The deposition rate constants in quartz sand were orders of magnitude below those expected from filtration theory, even in the absence of electrostatic energy barriers. The degree of hyperexponential deviation of the retained profiles from loglinear behavior did not decrease with increasing ionic strength in quartz sand. These observations demonstrate thatthe observed low adhesion and deviation from log-linear behavior was not driven by electrostatic repulsion. Measurements of the interaction forces between DA001 cells and the silicon nitride tip of an atomic force microscope (AFM) showed that the bacterium possesses surface polymers with an average equilibrium length of 59.8 nm. AFM adhesion force measurements revealed low adhesion affinities between silicon nitride and DA001 polymers with approximately 95% of adhesion forces having magnitudes < 0.8 nN. Steric repulsion due to surface polymers was apparently responsible for the low adhesion to silicon nitride, indicating that steric interactions from extracellular polymers controlled DA001 adhesion deficiency and deviation from log-linear behavior on quartz sand.

Agglomeration of a comprehensive model for the wind-driven sand transport at the Belgian Coast

NASA Astrophysics Data System (ADS)

Strypsteen, Glenn; Rauwoens, Pieter

2016-04-01

Although a lot of research has been done in the area of Aeolian transport, it is only during the last years that attention has been drawn to Aeolian transport in coastal areas. In these areas, the physical processes are more complex, due to a large number of transport limiting parameters. In this PhD-project, which is now in its early stage, a model will be developed which relates the wind-driven sand transport at the Belgian coast with physical parameters such as the wind speed, humidity and grain size of the sand, and the slope of beach and dune surface. For the first time, the interaction between beach and dune dynamics is studied at the Belgian coast. The Belgian coastline is only 67km long, but densely populated and therefore subject to coastal protection and safety. The coast mostly consists of sandy beaches and dikes. Although, still 33km of dunes exist, whose dynamics are far less understood. The overall research approach consists of three pathways: (i) field measurements, (ii) physical model tests, and (iii) numerical simulations. Firstly and most importantly, several field campaigns will provide accurate data of meteo-marine conditions, morphology, and sand transport events on a wide beach at the Belgian Coastline. The experimental set-up consists of a monitoring station, which will provide time series of vegetation cover, shoreline position, fetch distances, surficial moisture content, wind speed and direction and transport processes. The horizontal and vertical variability of the event scale Aeolian sand transport is analyzed with 8 MWAC sand traps. Two saltiphones register the intensity and variations of grain impacts over time. Two meteo-masts, each with four anemometers and one wind vane, provide quantitative measurements of the wind flow at different locations on the beach. Surficial moisture is measured with a moisture sensor. The topography measurements are typically done with laser techniques. To start, two sites are selected for measurement

Trajectories of saltating sand particles behind a porous fence

NASA Astrophysics Data System (ADS)

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

2015-01-01

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

Southern high latitude dune fields on Mars: Morphology, aeolian inactivity, and climate change

USGS Publications Warehouse

Fenton, L.K.; Hayward, R.K.

2010-01-01

In a study area spanning the martian surface poleward of 50?? S., 1190 dune fields have been identified, mapped, and categorized based on dune field morphology. Dune fields in the study area span ??? 116400km2, leading to a global dune field coverage estimate of ???904000km2, far less than that found on Earth. Based on distinct morphological features, the dune fields were grouped into six different classes that vary in interpreted aeolian activity level from potentially active to relatively inactive and eroding. The six dune field classes occur in specific latitude zones, with a sequence of reduced activity and degradation progressing poleward. In particular, the first signs of stabilization appear at ???60?? S., which broadly corresponds to the edge of high concentrations of water-equivalent hydrogen content (observed by the Neutron Spectrometer) that have been interpreted as ground ice. This near-surface ground ice likely acts to reduce sand availability in the present climate state on Mars, stabilizing high latitude dunes and allowing erosional processes to change their morphology. As a result, climatic changes in the content of near-surface ground ice are likely to influence the level of dune activity. Spatial variation of dune field classes with longitude is significant, suggesting that local conditions play a major role in determining dune field activity level. Dune fields on the south polar layered terrain, for example, appear either potentially active or inactive, indicating that at least two generations of dune building have occurred on this surface. Many dune fields show signs of degradation mixed with crisp-brinked dunes, also suggesting that more than one generation of dune building has occurred since they originally formed. Dune fields superposed on early and late Amazonian surfaces provide potential upper age limits of ???100My on the south polar layered deposits and ???3Ga elsewhere at high latitudes. No craters are present on any identifiable dune

Editorial - Special Issue on the Ninth International Conference on Aeolian Research - ICAR IX (Coastal Dune Processes and Aeolian Transport)

NASA Astrophysics Data System (ADS)

da Silva, Graziela Miot

2018-04-01

This special issue combines some of the papers related to coastal dune processes and aeolian sediment transport that were presented at the Ninth International Conference on Aeolian Research - ICAR IX. The conference was held between 4 and 8 of July 2016 in Mildura, Australia, organized by the International Society for Aeolian Research (ISAR) and convened by Adrian Chappell (Cardiff University), Craig Strong (Australian National University), Stephen Cattle (University of Sydney), Patrick Hesp (Flinders University), John Leys (New South Wales Office of Environment and Heritage), Lynda Petherick (University of Wellington) and Nick Webb (USDA-ARS Jornada Experimental Range).

Geochemical Identification of Windblown Dust Deposits in the Upper Permian Brushy Canyon Formation, Southern New Mexico

NASA Astrophysics Data System (ADS)

Tice, M. M.; Motanated, K.; Weiss, R.

2009-12-01

Windblown dust is a potentially important but difficult-to-quantify source of siliciclastics for sedimentary basins worldwide. Positively identifying windblown deposits requires distinguishing them from other low density suspension transport deposits. For instance, laminated very fine grained sandstones and siltstones of the Upper Permian Brushy Canyon Formation have been variously interpreted as 1) the deposits of slow-moving, low-density turbidity currents, 2) distal overbank deposits of turbidity currents, 3) the deposits of turbulent suspensions transported across a pycnocline (interflows), and 4) windblown dust. This facies forms the bulk of Brushy Canyon Formation slope deposits, so understanding its origin is critical to understanding the evolution of the basin as a whole. We use a geochemical mapping technique (x-ray fluorescence microscopy) to show that these rocks are up to two times enriched in very fine sand sized zircon and rutile grains relative to Bouma A divisions of interbedded turbidites, suggesting substantial turbulence during transport. However, in contrast with the A divisions, the laminated sandstones and siltstones never show evidence of scour or amalgamation, implying that flow turbulence did not interact with underlying beds. Moreover, proximal loess deposits are often characterized by elevated Zr/Al2O3. These observations are most consistent with windblown interpretations for Brushy Canyon Formation slope sediments, and suggest that evolution of this early deepwater slope system was controlled largely by short-distance aeolian transport of very fine sand and silt from the coast. Heavy mineral incorporation into Brushy Canyon Formation slope deposits as reflected in laminae-scale bulk Zr and Ti abundances may preserve a long-term record of local wind intensity during the Upper Permian.

Monitoring aeolian desertification process in Hulunbir grassland during 1975-2006, Northern China.

PubMed

Guo, Jian; Wang, Tao; Xue, Xian; Ma, Shaoxiu; Peng, Fei

2010-07-01

The Hulunbir grassland experienced aeolian desertification expansion during 1975-2000, but local rehabilitation during 2000-2006. Northern China suffered severe aeolian desertification during the past 50 years. Hulunbir grassland, the best stockbreeding base in Northern China, was also affected by aeolian desertification. To evaluate the evolution and status of aeolian desertification, as well as its causes, satellite images (acquired in 1975, 1984, 2000, and 2006) and meteorological and socioeconomic data were interpreted and analyzed. The results show there was 2,345.7, 2,899.8, 4,053.9, and 3,859.6 km(2) of aeolian desertified land in 1975, 1984, 2000, and 2006, respectively. The spatial pattern dynamic had three stages: stability during 1975-1984, fast expansion during 1984-2000, and spatial transfer during 2000-2006. The dynamic degree of aeolian desertification is negatively related to its severity. Comprehensive analysis shows that the human factor is the primary cause of aeolian desertification in Hulunbir grassland. Although aeolian desertified land got partly rehabilitated, constant increase of extremely severe aeolian desertified land implied that current measures were not effective enough on aeolian desertification control. Alleviation of grassland pressure may be an effective method.

Effect of different-sized colloids on the transport and deposition of titanium dioxide nanoparticles in quartz sand.

PubMed

Cai, Li; Peng, Shengnan; Wu, Dan; Tong, Meiping

2016-01-01

Colloids (non-biological and biological) with different sizes are ubiquitous in natural environment. The investigations regarding the influence of different-sized colloids on the transport and deposition behaviors of engineered-nanoparticles in porous media yet are still largely lacking. This study investigated the effects of different-sized non-biological and biological colloids on the transport of titanium dioxide nanoparticles (nTiO2) in quartz sand under both electrostatically favorable and unfavorable conditions. Fluorescent carboxylate-modified polystyrene latex microspheres (CML) with sizes of 0.2-2 μm were utilized as model non-biological colloids, while Gram-negative Escherichia coli (∼ 1 μm) and Gram-positive Bacillus subtilis (∼ 2 μm) were employed as model biological colloids. Under the examined solution conditions, both breakthrough curves and retained profiles of nTiO2 with different-sized CML particles/bacteria were similar as those without colloids under favorable conditions, indicating that the copresence of model colloids in suspensions had negligible effects on the transport and deposition of nTiO2 under favorable conditions. In contrast, higher breakthrough curves and lower retained profiles of nTiO2 with CML particles/bacteria relative to those without copresent colloids were observed under unfavorable conditions. Clearly, the copresence of model colloids increased the transport and decreased the deposition of nTiO2 in quartz sand under unfavorable conditions (solution conditions examined in present study). Both competition of deposition sites on quartz sand surfaces and the enhanced stability/dispersion of nTiO2 induced by copresent colloids were found to be responsible for the increased nTiO2 transport with colloids under unfavorable conditions. Moreover, the smallest colloids had the highest coverage on sand surface and most significant dispersion effect on nTiO2, resulting in the greatest nTiO2 transport. Copyright © 2015. Published

Sedimentary differentiation of aeolian grains at the White Sands National Monument, New Mexico, USA

NASA Astrophysics Data System (ADS)

Fenton, Lori K.; Bishop, Janice L.; King, Sara; Lafuente, Barbara; Horgan, Briony; Bustos, David; Sarrazin, Philippe

2017-06-01

Gypsum (CaSO4·2H2O) has been identified as a major component of part of Olympia Undae in the northern polar region of Mars, along with the mafic minerals more typical of Martian dune fields. The source and age of the gypsum is disputed, with the proposed explanations having vastly different implications for Mars' geological history. Furthermore, the transport of low density gypsum grains relative to and concurrently with denser grains has yet to be investigated in an aeolian setting. To address this knowledge gap, we performed a field study at White Sands National Monument (WSNM) in New Mexico, USA. Although gypsum dominates the bulk of the dune field, a dolomite-rich [CaMg(CO3)2] transport pathway along the northern border of WSNM provides a suitable analog site to study the transport of gypsum grains relative to the somewhat harder and denser carbonate grains. We collected samples along the stoss slope of a dune and on two coarse-grained ripples at the upwind margin of the dune field where minerals other than gypsum were most common. For comparison, additional samples were taken along the stoss slope of a dune outside the dolomite transport pathway, in the center of the dune field. Visible and near-infrared (VNIR), X-ray powder diffraction (XRD), and Raman analyses of different sample size fractions reveal that dolomite is only prevalent in grains larger than ∼1 mm. Other minerals, most notably calcite, are also present in smaller quantities among the coarse grains. The abundance of these coarse grains, relative to gypsum grains of the same size, drops off sharply at the upwind margin of the dune field. In contrast, gypsum dominated the finer fraction (<∼1 mm) at all sample sites, displaying no spatial variation. Estimates of sediment fluxes indicate that, although mineralogical differentiation of wind-transported grains occurs gradually in creep, the process is much more rapid when winds are strong enough to saltate the ⩾1 mm grains. The observed grain

Integrated Results from Analysis of the Rocknest Aeolian Deposit by the Curiosity Rover

NASA Technical Reports Server (NTRS)

Leshin, L. A.; Grotzinger, J. P.; Blake, D. F.; Edgett, K. S.; Gellert, R.; Mahaffy, P. R.; Malin, M. C.; Wiens, R. C.; Treiman, A. H.; Ming, D. W.;

Community variability of bacteria in alpine snow (Mont Blanc) containing Saharan dust deposition and their snow colonisation potential.

PubMed

Chuvochina, Maria S; Marie, Dominique; Chevaillier, Servanne; Petit, Jean-Robert; Normand, Philippe; Alekhina, Irina A; Bulat, Sergey A

2011-01-01

Microorganisms uplifted during dust storms survive long-range transport in the atmosphere and could colonize high-altitude snow. Bacterial communities in alpine snow on a Mont Blanc glacier, associated with four depositions of Saharan dust during the period 2006-2009, were studied using 16S rRNA gene sequencing and flow cytometry. Also, sand from the Tunisian Sahara, Saharan dust collected in Grenoble and Mont Blanc snow containing no Saharan dust (one sample of each) were analyzed. The bacterial community composition varied significantly in snow containing four dust depositions over a 3-year period. Out of 61 phylotypes recovered from dusty snow, only three phylotypes were detected in more than one sample. Overall, 15 phylotypes were recognized as potential snow colonizers. For snow samples, these phylotypes belonged to Actinobacteria, Proteobacteria and Cyanobacteria, while for Saharan sand/dust samples they belonged to Actinobacteria, Bacteroidetes, Deinococcus-Thermus and Proteobacteria. Thus, regardless of the time-scale, Saharan dust events can bring different microbiota with no common species set to alpine glaciers. This seems to be defined more by event peculiarities and aeolian transport conditions than by the bacterial load from the original dust source.

Behavior of Windblown Sand on Mars: Results From Single-Particle Experiments

NASA Astrophysics Data System (ADS)

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

1996-03-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG & G Program.

Late Quaternary paleoenvironments and paleoclimatic conditions in the distal Andean piedmont, southern Mendoza, Argentina

NASA Astrophysics Data System (ADS)

Tripaldi, Alfonsina; Zárate, Marcelo A.; Brook, George A.; Li, Guo-Qiang

2011-09-01

The Andean piedmont of Mendoza is a semiarid region covered by extensive and partially vegetated dune fields consisting of mostly inactive aeolian landforms of diverse size and morphology. This paper is focused on the San Rafael plain (SRP) environment, situated in the distal Andean piedmont of Mendoza (34° 30'S), and reports the sedimentology and OSL chronology of two representative exposures of late Quaternary deposits, including their paleoenvironmental and paleoclimatic significance. Eleven facies, including channel, floodplain, fluvio-aeolian interaction, and reworked pyroclastic and aeolian deposits, were described and grouped into two facies associations (FA1 and FA2). FA1 was formed by unconfined sheet flows, minor channelized streams and fluvial-aeolian interaction processes. FA2 was interpreted as aeolian dune and sand-sheet deposits. OSL chronology from the SRP sedimentary record indicates that between ca. 58-39 ka and ca. 36-24 ka (MIS 3), aggradation was governed by ephemeral fluvial processes (FA1) under generally semiarid conditions. During MIS 2, the last glacial maximum (ca. 24-12 ka), a major climatic shift to more arid conditions is documented by significant aeolian activity (FA2) that became the dominant sedimentation process north of the Diamante-Atuel fluvial system. The inferred paleoenvironmental conditions from the SRP sections are in broad agreement with regional evidence.

Environmental consequences of oil production from oil sands

NASA Astrophysics Data System (ADS)

Rosa, Lorenzo; Davis, Kyle F.; Rulli, Maria C.; D'Odorico, Paolo

2017-02-01

Crude oil from oil sands will constitute a substantial share of future global oil demand. Oil sands deposits account for a third of globally proven oil reserves, underlie large natural forested areas, and have extraction methods requiring large volumes of freshwater. Yet little work has been done to quantify some of the main environmental impacts of oil sands operations. Here we examine forest loss and water use for the world's major oil sands deposits. We calculate actual and potential rates of water use and forest loss both in Canadian deposits, where oil sands extraction is already taking place, and in other major deposits worldwide. We estimated that their exploitation, given projected production trends, could result in 1.31 km3 yr-1 of freshwater demand and 8700 km2 of forest loss. The expected escalation in oil sands extraction thus portends extensive environmental impacts.

The Karakum and Kyzylkum sand seas dynamics; mapping and palaeoclimatic interpretations

NASA Astrophysics Data System (ADS)

Maman, Shimrit; Blumberg, Dan G.; Tsoar, Haim; Porat, Naomi

2015-04-01

Sand seas are large basins in deserts that are mantled by wind-swept sand and that exhibit varying degrees of vegetation cover. Wilson (1973) was the first to globally map and classify sand seas. Beyond Wilson's maps, however, little research has been published regarding the Karakum and Kyzylkum sand seas of Central Asia. Wilson's maps delineate active ergs from inactive ergs based solely on precipitation. His assumption of annual average rainfall as a factor determining mobility vs. stability of sand seas is too simplistic and does not take into consideration other factors such as biogenic soil crusts and wind power, both of which are known to have major effects on the dynamics of sand dunes. Literature related to mapping and classifying the Central Asian ergs by remote sensing or sand sea classification state (stable/active) is lacking. Moreover, the palaeoclimatic significance of dunes in Central Asia is difficult to assess, as there has been few studies of dune stratigraphy and numerical ages are lacking. Optically stimulated luminescence (OSL) is a firm optical dating method that is used to determine the elapsed time since quartz grains were last exposed to sunlight, thus, their burial. Yet, absolute ages indicating mobilization and stabilization of these sands, are still inadequately known and are here under discussion. The broad concern of this research was to determine the dynamics of the Central Asian sand seas and study the palaeoclimatic changes that brought to their stabilization. As there are no reliable maps or aeolian discussion of these sands, establishment of a digital data base was initially conducted, focusing on identifying and mapping these sand seas. The vast area and inaccessibility make traditional mapping methods virtually impossible. A variety of space-borne imagery both optical and radar, with varying spectral and spatial resolutions was used. These images provided the basis for mapping sand distribution, dune forms, and vegetation cover

The response of source-bordering aeolian dunefields to sediment-supply changes 2: Controlled floods of the Colorado River in Grand Canyon, Arizona, USA

USGS Publications Warehouse

Sankey, Joel B.; Caster, Joshua; Kasprak, Alan; East, Amy

2018-01-01

In the Colorado River downstream of Glen Canyon Dam in the Grand Canyon, USA, controlled floods are used to resupply sediment to, and rebuild, river sandbars that have eroded severely over the past five decades owing to dam-induced changes in river flow and sediment supply. In this study, we examine whether controlled floods, can in turn resupply aeolian sediment to some of the large source-bordering aeolian dunefields (SBDs) along the margins of the river. Using a legacy of high-resolution lidar remote-sensing and meteorological data, we characterize the response of four SBDs (a subset of 117 SBDs and other aeolian-sand-dominated areas in the canyon) during four sediment-laden controlled floods of the Colorado River in 2012, 2013, 2014, and 2016. We find that aeolian sediment resupply unambiguously occurred in 8 of the 16 instances of controlled flooding adjacent to SBDs. Resupply attributed to individual floods varied substantially among sites, and occurred with four, three, one, and zero floods at the four sites, respectively. We infer that the relative success of controlled floods as a regulated-river management tool for resupplying sediment to SBDs is analogous to the frequency of resupply observed for fluvial sandbars in this setting, in that sediment resupply was estimated to have occurred for roughly half of the instances of recent controlled flooding at sandbars monitored separately from this study. We find the methods developed in this, and a companion study, are effective tools to quantify geomorphic changes in sediment storage, along linked fluvial and aeolian pathways of sedimentary systems.

The response of source-bordering aeolian dunefields to sediment-supply changes 2: Controlled floods of the Colorado River in Grand Canyon, Arizona, USA

NASA Astrophysics Data System (ADS)

Sankey, Joel B.; Caster, Joshua; Kasprak, Alan; East, Amy E.

2018-06-01

In the Colorado River downstream of Glen Canyon Dam in the Grand Canyon, USA, controlled floods are used to resupply sediment to, and rebuild, river sandbars that have eroded severely over the past five decades owing to dam-induced changes in river flow and sediment supply. In this study, we examine whether controlled floods, can in turn resupply aeolian sediment to some of the large source-bordering aeolian dunefields (SBDs) along the margins of the river. Using a legacy of high-resolution lidar remote-sensing and meteorological data, we characterize the response of four SBDs (a subset of 117 SBDs and other aeolian-sand-dominated areas in the canyon) during four sediment-laden controlled floods of the Colorado River in 2012, 2013, 2014, and 2016. We find that aeolian sediment resupply unambiguously occurred in 8 of the 16 instances of controlled flooding adjacent to SBDs. Resupply attributed to individual floods varied substantially among sites, and occurred with four, three, one, and zero floods at the four sites, respectively. We infer that the relative success of controlled floods as a regulated-river management tool for resupplying sediment to SBDs is analogous to the frequency of resupply observed for fluvial sandbars in this setting, in that sediment resupply was estimated to have occurred for roughly half of the instances of recent controlled flooding at sandbars monitored separately from this study. We find the methods developed in this, and a companion study, are effective tools to quantify geomorphic changes in sediment storage, along linked fluvial and aeolian pathways of sedimentary systems.

Atmospheric dry deposition of sulfur and nitrogen in the Athabasca Oil Sands Region, Alberta, Canada

Treesearch

Yu-Mei Hsu; Andrzej Bytnerowicz; Mark E. Fenn; Kevin E. Percy

2016-01-01

Due to the potential ecological effects on terrestrial and aquatic ecosystems from atmospheric deposition in the Athabasca Oil Sands Region (AOSR), Alberta, Canada, this study was implemented to estimate atmospheric nitrogen (N) and sulfur (S) inputs. Passive samplers were used to measure ambient concentrations of ammonia (NH3), nitrogen dioxide...

Coastal dune dynamics in response to excavated foredune notches

NASA Astrophysics Data System (ADS)

Ruessink, B. G.; Arens, S. M.; Kuipers, M.; Donker, J. J. A.

2018-04-01

Dune management along developed coasts has traditionally focussed on the suppression of the geomorphic dynamics of the foredune to improve its role in sea defence. Because a stabilized foredune acts as an almost total barrier to aeolian transport from the beach, the habitat diversity in the more landward dunes has degraded. With the overarching objective to mitigate this undesirable loss in biodiversity, dune management projects nowadays increasingly intend to restore aeolian dynamics by reconnecting the beach-dune system with notches excavated through the foredune. Here, we use repeat topographic survey data to examine the geomorphic response of a coastal dune system in the Dutch National Park Zuid-Kennemerland to five notches excavated in 2012-2013 within an 850-m stretch of the 20-m high established foredune. The notches were dug in a V-shape (viewed onshore), with a width between approximately 50 and 100 m at the top, a (cross-dune) length between 100 and 200 m, and excavation depths between 9 and 12.5 m. The 1 × 1 m digital terrain models, acquired with airborne Lidar and UAV photogrammetry, illustrate that during the 3-year survey period the notches developed into a U-shape because of wall deflation, and that up to 8-m thick and 150-m long depositional lobes formed landward of the notches. Sand budget computations showed that the sand volume of the entire study area increased by about 22,750 m3/year, which, given the 850-m width of the study area, corresponds to an aeolian input from the beach of approximately 26.5 m3/m/year. Between 2006 and 2012 all wind-blown beach sand deposited on the seaward side of the foredune; since 2013, the notches have caused 75% of the sand to be deposited landward of the foredune. This highlights that the notches are highly effective conduits for aeolian transport into the back dunes. Future monitoring is required to determine for how long the notches will stimulate aeolian dynamics and if (and when) vegetation eventually

Techniques for assessing sand and gravel resources in glaciofluvial deposits; an example using the surficial geologic map of the Loudon Quadrangle, Merrimack and Belknap counties, New Hampshire

USGS Publications Warehouse

Sutphin, David M.; Drew, Lawrence J.; Fowler, Brian K.; Goldsmith, Richard

2002-01-01

A method for estimating the sand and gravel resources in glaciofluvial systems has been developed based on surficial mapping techniques that use the morphosequence concept and geographic information systems (GIS). Two different strategies are used to estimate gravel resources. One strategy estimates the sand and gravel resources contained in esker deposits; the other, which is more dependent on GIS, estimates resources in non-esker deposits. An attempt has been made to determine which deposits are sterilized; that is, those beneath the water table, adjacent to streams or roads, or encroached on by urbanization. Preliminary estimates using these methods indicate that about 158,000,000 m3 (206,000,000 yd3) of sand and gravel are present in the Soucook River valley part of the Loudon, N.H., 7.5-minute quadrangle. About 64,500,000 m3 (84,400,000 yd3) of these materials are in deposits above the water table. About 26 percent of the sand and gravel resources above the water table are unlikely to be mined because they have been sterilized. Of the remaining resources, 479,000 m3 (627,000 yd3) of gravel and 1,120,000 m3 (1,460,000 yd3) of sand are in esker deposits, and 9,400,000 m3 (12,300,000 yd3) of gravel and 38,300,000 m3 (50,100,000 yd3) of sand are in stratified non-esker deposits. With the addition of new well data, newer and more accurate estimates are possible.

Natural radioactivity of the tar-sand deposits of Ondo State, Southwestern Nigeria

NASA Astrophysics Data System (ADS)

Fasasi, M. K.; Oyawale, A. A.; Mokobia, C. E.; Tchokossa, P.; Ajayi, T. R.; Balogun, F. A.

2003-06-01

A combination of gamma spectrometry and energy dispersive X-ray fluorescence was used to determine the presence and level of radioactivity of radionuclides in bituminous sand and overburden obtained from bituminous sand deposits in Ondo State Nigeria for the purpose of providing baseline data and assessing its impact on the environment. The radionuclides identified with reliable regularity belong to the decay series of naturally occurring radionuclides headed by 238U and 232Th. The non-decay series of naturally occurring 40K was found to be below the limit of detection. The average specific activity concentration values obtained for 214 Bi, 208Tl, and 226Ra in the overburden are 165.64±2.91, 150.25±2.91 and 60.97±2.27 Bq kg -1, respectively. The measured activity in the bituminous sand layer is so low that it can be said to be non-radioactive. The result of the EDXRF supports the presence of radioelements in the overburden, which are likely to be embedded in accessory minerals like zircon and tourmaline. Thus, surface exploration technique using soil-gas radon measurement will not yield the desired result. Furthermore, the level of radioelements and associated decay daughter 222Rn is not expected to cause any health hazard.

Aeolian transport of biota with dust: A wind tunnel experiment

NASA Astrophysics Data System (ADS)

Rivas, J. A., Jr.; Gill, T. E.; Van Pelt, R. S.; Walsh, E.

2015-12-01

Ephemeral wetlands are ideal sources for dust emission, as well as repositories for dormant stages of aquatic invertebrates. An important component of invertebrate dispersal and colonization to new areas is the ability to be entrained into the atmosphere. Aquatic invertebrate eggs fall within the size of dust and sand grains (30-600μm), are less dense and aerodynamically shaped. We have shown previously that aquatic invertebrates can be dispersed long distances in dust storms but the extent of transport of taxa based on diapausing egg size/morphology has not been investigated. Here, we control the wind erosion process in a wind tunnel to test entrainment of diapausing stages of brine shrimp, clam shrimp, tadpole shrimp, fairy shrimp, Daphnia, and the rotifers Brachionus plicatilis and B. calyciflorus into the air by saltation. Diapausing eggs were mixed with sterilized wind-erodible soil. The soil/egg mixture was moistened with distilled water and air dried to form a crust. Dust was generated in a wind tunnel by releasing sand grains that act as saltator material similar to wind-entrained natural sands. Maximum wind velocity was 10m/s and entrained particles were sampled through an isokinetic horizontal intake opening. Aeolian sediment was collected from three points in the system; transfer section for coarse sediment, the pan subtending a settling chamber for finer saltation-sized sediment, and two paper filters for suspension-sized sediment. Samples were then passed through 250 and 350 μm sieves to remove abrader sand and rehydrated with various sterile media depending on the type of organism. We retrieved viable brine, fairy, and tadpole shrimp, ostracods, Daphnia, and diapausing eggs of the rotifers after hydration. This experiment demonstrates that resting stages of many invertebrates can be wind-eroded due to size and egg morphology and remain viable under controlled conditions mimicking dust emission.

Modeling of Grain Size Distribution of Tsunami Sand Deposits in V-shaped Valley of Numanohama During the 2011 Tohoku Tsunami

NASA Astrophysics Data System (ADS)

Gusman, A. R.; Satake, K.; Goto, T.; Takahashi, T.

2016-12-01

Estimating tsunami amplitude from tsunami sand deposit has been a challenge. The grain size distribution of tsunami sand deposit may have correlation with tsunami inundation process, and further with its source characteristics. In order to test this hypothesis, we need a tsunami sediment transport model that can accurately estimate grain size distribution of tsunami deposit. Here, we built and validate a tsunami sediment transport model that can simulate grain size distribution. Our numerical model has three layers which are suspended load layer, active bed layer, and parent bed layer. The two bed layers contain information about the grain size distribution. This numerical model can handle a wide range of grain sizes from 0.063 (4 ϕ) to 5.657 mm (-2.5 ϕ). We apply the numerical model to simulate the sedimentation process during the 2011 Tohoku earthquake in Numanohama, Iwate prefecture, Japan. The grain size distributions at 15 sample points along a 900 m transect from the beach are used to validate the tsunami sediment transport model. The tsunami deposits are dominated by coarse sand with diameter of 0.5 - 1 mm and their thickness are up to 25 cm. Our tsunami model can well reproduce the observed tsunami run-ups that are ranged from 16 to 34 m along the steep valley in Numanohama. The shapes of the simulated grain size distributions at many sample points located within 300 m from the shoreline are similar to the observations. The differences between observed and simulated peak of grain size distributions are less than 1 ϕ. Our result also shows that the simulated sand thickness distribution along the transect is consistent with the observation.

A reappraisal of the stratigraphy and chronology of Early Pliocene palaeontological sites from Lanzarote Island containing fossil terrestrial animals

NASA Astrophysics Data System (ADS)

Lomoschitz, Alejandro; Sánchez Marco, Antonio; Huertas, María José; Betancort, Juan F.; Isern, Arnau; Sanz, Elena; Meco, Joaquín

2016-11-01

The Famara massif, in the north of Lanzarote Island, constitutes the remains of a former island inhabited by the oldest known vertebrate fauna of the Canary archipelago off the coast of Africa. In this study, new ages are offered for the underlying and overlying basaltic lava flows of two paleontological sites. The island's three major palaeontological sites, which contain remains of this ancient fauna (Valle Grande, Valle Chico and Fuente de Gusa), are intercorrelated according to their lithologies, sedimentology, palaeontological content and geochronology. The new K/Ar age interval for the fossiliferous sedimentary deposits ranges between 4.3 ± 0.7 and 3.78 ± 0.71 Ma, within the Early Pliocene, and shows that the first known terrestrial animals in Lanzarote were present on the island for about 500 ka. The principal component of the deposits is a bioclastic calcarenite of aeolian origin (sand sheet deposits), which is present in all three sites and constitutes 65% of the beds. The remaining 35% is of fluvial-aeolian origin (mainly stream deposits). All the beds contain the same fossils (insect egg pods, land snails, avian eggshells and tortoise eggshells). The local palaeogeography and the formation of the deposits were conditioned by a flat plain, larger than 16 km2, over which aeolian sands moved freely with a prevailing NNE-WSW wind direction. In agreement with previous investigations, the palaeoclimate in this interval (ca. 4.3 to 3.8 Ma) must have been mainly dry with some rainy episodes.

Late Pleistocene dune-sourced alluvial fans in coastal settings: Sedimentary facies and related processes (Mallorca, Western Mediterranean)

NASA Astrophysics Data System (ADS)

Pomar, F.; del Valle, L.; Fornós, J. J.; Gómez-Pujol, L.

2018-05-01

Aeolian-alluvial sedimentary interaction results in the formation of deposits characterized by typical alluvial sedimentary structures, but is composed of conspicuous amounts of aeolian sediments. The literature on this topic is limited and most works relate more with continental aeolian dunes or fluvial dune interference with fan bodies. Furthermore, there is a lack of examples of aeolian-alluvial sedimentary interference in coastal settings. In the western Mediterranean, there are many Pleistocene alluvial fan deposits built up partly by sediment originating from coastal dunes dismantled by alluvial streams. Very often, these deposits show a continuous sedimentary sequence through which we can derive the contribution and predominance of coastal, alluvial-colluvial and aeolian processes and their controls on landscape formation. This is an outstanding feature within coastal systems since it shows marine sediments reworked and integrated within coastal dune fields by aeolian transport, and the latter built up into alluvial fan bodies. In this sense, aeolian-alluvial interaction is the geomorphic-sedimentary expression of the coexistence and overlapping of alluvial and aeolian environments resulting in deposits sharing sedimentary features from both environments. The aim of this paper is to unravel the contribution of coastal dunes in the construction of alluvial fans bodies and identify the main sedimentary facies that constitute these deposits, as well as their climatic controls. For this reason, Es Caló fan (northern Mallorca) has been selected due to its well-exposed deposits exhibiting the alternation of aeolian, alluvial and colluvial deposits. Sedimentological and stratigraphic analyses based on 33 logs and complementary analyses demonstrate that most of the facies constituting the fan body are made up completely of marine bioclastic sands. These deposits record an alluvial fan sedimentary environment characterized by sediments inputs that do not proceed

Sulfur Biogeochemistry of an Oil Sands Composite Tailings Deposit

PubMed Central

Warren, Lesley A.; Kendra, Kathryn E.; Brady, Allyson L.; Slater, Greg F.

2016-01-01

Composite tailings (CT), an engineered, alkaline, saline mixture of oil sands tailings (FFT), processed sand and gypsum (CaSO4; 1 kg CaSO4 per m3 FFT) are used as a dry reclamation strategy in the Alberta Oil Sands Region (AOSR). It is estimated that 9.6 × 108 m3 of CT are either in, or awaiting emplacement in surface pits within the AOSR, highlighting their potential global importance in sulfur cycling. Here, in the first CT sulfur biogeochemistry investigation, integrated geochemical, pyrosequencing and lipid analyses identified high aqueous concentrations of ∑H2S (>300 μM) and highly altered sulfur compounds composition; low cell biomass (3.3 × 106– 6.0 × 106 cells g−1) and modest bacterial diversity (H' range between 1.4 and 1.9) across 5 depths spanning 34 m of an in situ CT deposit. Pyrosequence results identified a total of 29,719 bacterial 16S rRNA gene sequences, representing 131 OTUs spanning19 phyla including 7 candidate divisions, not reported in oil sands tailings pond studies to date. Legacy FFT common phyla, notably, gamma and beta Proteobacteria, Firmicutes, Actinobacteria, and Chloroflexi were represented. However, overall CT microbial diversity and PLFA values were low relative to other contexts. The identified known sulfate/sulfur reducing bacteria constituted at most 2% of the abundance; however, over 90% of the 131 OTUs identified are capable of sulfur metabolism. While PCR biases caution against overinterpretation of pyrosequence surveys, bacterial sequence results identified here, align with phospholipid fatty acid (PLFA) and geochemical results. The highest bacterial diversities were associated with the depth of highest porewater [∑H2S] (22–24 m) and joint porewater co-occurrence of Fe2+ and ∑H2S (6–8 m). Three distinct bacterial community structure depths corresponded to CT porewater regions of (1) shallow evident Fe(II) (<6 m), (2) co-occurring Fe(II) and ∑H2S (6–8 m) and (3) extensive ∑H2S (6–34 m) (Uni

Monitoring Sand Sheets and Dunes

NASA Image and Video Library

2017-06-12

NASA's Mars Reconnaissance Orbiter (MRO) captured this crater featuring sand dunes and sand sheets on its floor. What are sand sheets? Snow fall on Earth is a good example of sand sheets: when it snows, the ground gets blanketed with up to a few meters of snow. The snow mantles the ground and "mimics" the underlying topography. Sand sheets likewise mantle the ground as a relatively thin deposit. This kind of environment has been monitored by HiRISE since 2007 to look for movement in the ripples covering the dunes and sheets. This is how scientists who study wind-blown sand can track the amount of sand moving through the area and possibly where the sand came from. Using the present environment is crucial to understanding the past: sand dunes, sheets, and ripples sometimes become preserved as sandstone and contain clues as to how they were deposited The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 25 centimeters (9.8 inches) per pixel (with 1 x 1 binning); objects on the order of 75 centimeters (29.5 inches) across are resolved.] North is up. https://photojournal.jpl.nasa.gov/catalog/PIA21757

Modeling aeolian dune and dune field evolution

NASA Astrophysics Data System (ADS)

Diniega, Serina

Aeolian sand dune morphologies and sizes are strongly connected to the environmental context and physical processes active since dune formation. As such, the patterns and measurable features found within dunes and dune fields can be interpreted as records of environmental conditions. Using mathematical models of dune and dune field evolution, it should be possible to quantitatively predict dune field dynamics from current conditions or to determine past field conditions based on present-day observations. In this dissertation, we focus on the construction and quantitative analysis of a continuum dune evolution model. We then apply this model towards interpretation of the formative history of terrestrial and martian dunes and dune fields. Our first aim is to identify the controls for the characteristic lengthscales seen in patterned dune fields. Variations in sand flux, binary dune interactions, and topography are evaluated with respect to evolution of individual dunes. Through the use of both quantitative and qualitative multiscale models, these results are then extended to determine the role such processes may play in (de)stabilization of the dune field. We find that sand flux variations and topography generally destabilize dune fields, while dune collisions can yield more similarly-sized dunes. We construct and apply a phenomenological macroscale dune evolution model to then quantitatively demonstrate how dune collisions cause a dune field to evolve into a set of uniformly-sized dunes. Our second goal is to investigate the influence of reversing winds and polar processes in relation to dune slope and morphology. Using numerical experiments, we investigate possible causes of distinctive morphologies seen in Antarctic and martian polar dunes. Finally, we discuss possible model extensions and needed observations that will enable the inclusion of more realistic physical environments in the dune and dune field evolution models. By elucidating the qualitative and

Introducing a New International Society of Aeolian Research

USDA-ARS?s Scientific Manuscript database

Aeolian research is long-standing and rapidly growing area of study where scientists of many disciplines meet to investigate the effects of wind on the surface of the Earth and other planetary bodies, such as Mars and Titan. Fields of study in aeolian research cover a broad spectrum ranging from dev...

A multi-isotope approach for assessing industrial contributions to atmospheric nitrogen deposition in the Athabasca oil sands region in Alberta, Canada

Treesearch

Bernadette C. Proemse; Bernhard Mayer; Mark E. Fenn; Christopher S. Ross

2013-01-01

Industrial nitrogen (N) emissions in the Athabasca oil sands region (AOSR), Alberta, Canada, affect nitrate (NO3) and ammonium (NH4) deposition rates in close vicinity of industrial emitters. NO3-N and NH4-N open field and throughfall deposition rates were determined at various...

Lunar and Planetary Science XXXV: Mars: Wind, Dust Sand, and Debris

NASA Technical Reports Server (NTRS)

2004-01-01

The session "Mars: Wind, Dust Sand, and Debris" included: Mars Exploration Rovers: Laboratory Simulations of Aeolian Interactions; Thermal and Spectral Analysis of an Intracrater Dune Field in Amazonis Planitia; How High is that Dune? A Comparison of Methods Used to Constrain the Morphometry of Aeolian Bedforms on Mars; Dust Devils on Mars: Scaling of Dust Flux Based on Laboratory Simulations; A Close Encounter with a Terrestrial Dust Devil; Interpretation of Wind Direction from Eolian Features: Herschel Crater, Mars Erosion Rates at the Viking 2 Landing Site; Mars Dust: Characterization of Particle Size and Electrostatic Charge Distributions; Simple Non-fluvial Models of Planetary Surface Modification, with Application to Mars; Comparison of Geomorphically Determined Winds with a General Circulation Model: Herschel Crater, Mars; Analysis of Martian Debris Aprons in Eastern Hellas Using THEMIS; Origin of Martian Northern Hemisphere Mid-Latitude Lobate Debris Aprons; Debris Aprons in the Tempe/Mareotis Region of Mars;and Constraining Flow Dynamics of Mass Movements on Earth and Mars.

Mid-Holocene stabilization of the Karakum and Kyzylkum sand seas, central Asia - evidence from OSL ages

NASA Astrophysics Data System (ADS)

Maman, Shimrit; Tsoar, Haim; Blumberg, Dan G.; Porat, Naomi

2013-04-01

Sand seas (ergs) are large areas of deserts covered by wind-swept sand with varying degrees of vegetation cover. The Kyzylkum and Karakum ergs have accumulated in the Turan basin, northwest of the Hindu Kush range, and span from south Turkmenistan to the Syrdarya River in Kazakhstan. These ergs are dissected by the Amudarya River; To the north lies the Kyzylkum (red sands) and to the south the Karakum (black sands). This area is understudied, and little information has been published regarding the sands stabilization processes and deposition ages. This research focuses on identifying and mapping the ergs of Central Asia and analyzing the climate factors that set the dunes into motion and that stabilized them. A variety of spaceborne imagery with varying spectral and spatial resolutions was used. These images provide the basis for mapping sand distribution, dune forms, and vegetation cover. Wilson (1973) defined these ergs as active based on precipitation. Our results show that they are mostly stabilized, with an estimated area of ~260,000 sq. Km for Kara-Kum , and ~195,500 sq. Km for the Kyzyl-Kum . Meteorological analysis of wind and precipitation data indicate a low wind energy environment (DP<200) and sufficient rainfall (>100 mm) to which is essential for vegetation cover. We present the first optically stimulated luminescence (OSL) ages from the upper meter of 14 exposed sections from both ergs. The age of the sand samples was determined as ~Mid-Holocene by OSL, which provides an insight into past climate characteristics. These ages indicate extensive sand and dune stabilization during the Mid-Holocene. GIS analysis was performed in parallel with field work to validate and verify the results. The OSL ages, coupled with a compilation of regional palaeoclimatic data, corroborate and reinforce the previously proposed Mid-Holocene Liavliakan phase, known to reflect a warmer, wetter, less windy climate than persists today and that resulted in dune stabilization

Vertical ground motion and its effects on liquefaction resistance of fully saturated sand deposits

PubMed Central

Kontoe, Stavroula; Taborda, David M. G.; Potts, David M.

2016-01-01

Soil liquefaction has been extensively investigated over the years with the aim to understand its fundamental mechanism and successfully remediate it. Despite the multi-directional nature of earthquakes, the vertical seismic component is largely neglected, as it is traditionally considered to be of much lower amplitude than the components in the horizontal plane. The 2010–2011 Canterbury earthquake sequence in New Zealand is a prime example that vertical accelerations can be of significant magnitude, with peak amplitudes well exceeding their horizontal counterparts. As research on this topic is very limited, there is an emerging need for a more thorough investigation of the vertical motion and its effect on soil liquefaction. As such, throughout this study, uni- and bidirectional finite-element analyses are carried out focusing on the influence of the input vertical motion on sand liquefaction. The effects of the frequency content of the input motion, of the depth of the deposit and of the hydraulic regime, using variable permeability, are investigated and exhaustively discussed. The results indicate that the usual assumption of linear elastic response when compressional waves propagate in a fully saturated sand deposit does not always hold true. Most importantly post-liquefaction settlements appear to be increased when the vertical component is included in the analysis. PMID:27616931

Vertical ground motion and its effects on liquefaction resistance of fully saturated sand deposits.

PubMed

Tsaparli, Vasiliki; Kontoe, Stavroula; Taborda, David M G; Potts, David M

2016-08-01

Soil liquefaction has been extensively investigated over the years with the aim to understand its fundamental mechanism and successfully remediate it. Despite the multi-directional nature of earthquakes, the vertical seismic component is largely neglected, as it is traditionally considered to be of much lower amplitude than the components in the horizontal plane. The 2010-2011 Canterbury earthquake sequence in New Zealand is a prime example that vertical accelerations can be of significant magnitude, with peak amplitudes well exceeding their horizontal counterparts. As research on this topic is very limited, there is an emerging need for a more thorough investigation of the vertical motion and its effect on soil liquefaction. As such, throughout this study, uni- and bidirectional finite-element analyses are carried out focusing on the influence of the input vertical motion on sand liquefaction. The effects of the frequency content of the input motion, of the depth of the deposit and of the hydraulic regime, using variable permeability, are investigated and exhaustively discussed. The results indicate that the usual assumption of linear elastic response when compressional waves propagate in a fully saturated sand deposit does not always hold true. Most importantly post-liquefaction settlements appear to be increased when the vertical component is included in the analysis.

Mineral resource of the month: industrial sand and gravel

USGS Publications Warehouse

Dolley, Thomas

2007-01-01

With many diverse uses, industrial sand and gravel, also known as silica sand, is one of the most important nonmetallic minerals in the world. Industrial sand and gravel is a mining industry term used for sands that have a very high percentage of silicon dioxide, or greater than 95 percent quartz. Deposits of industrial sand and gravel can be found virtually everywhere on Earth, but are less widespread than deposits of common construction sand and gravel. Industrial sand and gravel is distinctive in grain size, hardness, inertness and resistance to high temperature and chemical action. Beverage containers, fiberglass insulation, fiber-optic cables and light bulbs are just some of today’s many products produced from industrial sand and gravel.

A study of the management strategies for river aeolian dust inhibition at the estuary of Zhuo-shui River

NASA Astrophysics Data System (ADS)

Tsai, S. F.; Lin, C. Y.

2014-12-01

With the characteristics of humidity in summer and drought in winter, there existing lots of bare lands due to the decline of water level cause large amounts of aeolian dust and environmental deterioration during the monsoon seasons in central Taiwan. How to adopt effective measures to inhibit the damage of dust is an essential issue. This study selected the serious dust-affected section of Zhuo-shui river (bridge Zi-qiang to Xi-bin) to delineate the areas of potential aeolian dust occurrence, explore the relationship between elevation and water level determined from return period analysis, submit the countermeasures for dust inhibition at the bare lands and/or cultivated areas, and address the responsibilities of related authority offices for dust prevention by means of literature review. The return period of inundation for the areas of potential aeolian dust occurrence is 1.1 years. Engineering of dust prevention with highly unit price are not recommended due to could be destroyed annually. The deposition sites of a river are usually located at the convex bank, which with silt texture and high salinity are not suitable for cultivation, are delineated as the areas of potential aeolian dust occurrence. Besides technology consideration in dust prevention, this study also examined the related articles of river management to integrate a comprehensive vision for better riverside environment and air quality.

The birth and death of transverse aeolian ridges on Mars

USGS Publications Warehouse

Geissler, Paul E.

2014-01-01

Transverse aeolian ridges (TARs) are small bright windblown deposits found throughout the Martian tropics that stand a few meters tall and are spaced a few tens of meters apart. The origin of these features remains mysterious more than 20 years after their discovery on Mars. This paper presents a new hypothesis, that some of the TARs could be indurated dust deposits emplaced millions of years ago during periods of higher axial obliquity. It suggests that these TARs are primary depositional bed forms that accumulated in place from dust carried by the winds in suspension, perhaps in a manner comparable to antidunes on Earth, and were subsequently indurated and eroded to their current states by eons of sandblasting. It points out examples of modern dust drifts and dune-like features that appear to have been recently formed by dust accumulating directly onto the surface from atmospheric suspension. It shows how these pristine dust deposits could evolve to explain the range of morphologies of the TARs. Finally, it explains how the known properties of many TARs are consistent with this hypothesis, including their composition, thermal behavior, and distribution.

Early-stage aeolian protodune development and migration

NASA Astrophysics Data System (ADS)

Nield, J. M.; Baddock, M. C.; Wiggs, G.

2017-12-01

Early-stage bedforms, or protodunes, can be observed to form on sandy beaches, desert gravels or superimposed on the surfaces of larger dunes and can develop topography of 0.1 m or more over several hours. These protodunes are the precursors to embryo and eventually mature dunes, and so it is important to understand how feedbacks between flow, transport and form contribute to this development sequence. Whilst theory and conceptual models have offered some explanation for protodune existence and development, we know surprisingly little about how these bedforms initiate and migrate because it is difficult to measure small changes in form (millimetres; seconds) on highly active surfaces of limited topographic expression. Here, we employ terrestrial laser scanning (TLS) to measure morphological change at the high frequency and spatial resolution (sub-millimetre) required to gain new insights into protodune behaviour. Along with TLS derived saltation and surface moisture, additional sediment flux and windspeed measurements help to elucidate how the protodune topography interacts with airflow and sand transport. We focus on a number of coastal bedforms in various development stages including a 0.06 m high protodune which grew vertically by 0.005 m in two hours with the switch from erosion to deposition identified to occur at a point 0.07 m upwind of the crest. This growth was associated with a reduction in time-averaged sediment flux of 18% over the crestal region. We also observed a decline in lower stoss slope steepness (by 3°) and a steepening of the lee slope, indicating a reshaping of initial protodune form towards the morphology of a more mature dune. Our findings highlight the crucial role of form-flow feedbacks, even on very small bedforms, in driving early-stage bedform growth and development, and show how the use of high resolution TLS to measure both surface topography and grains moving above the surface, can offer new insights into a long standing deficiency

Interglacial-glacial cycles recorded in the deposit sequence at Kruzhyky on the Dniester River (East Carpathian Foreland)

NASA Astrophysics Data System (ADS)

Łanczont, Maria; Boguckyj, Aandrij; Mroczek, Przemysław; Zieliński, Paweł; Jacyszyn, Andrij; Pidek, Agnieszka I.; Urban, Danuta; Kulesza, Piotr; Hołub, Beata

2010-01-01

Palaeogeographic investigations were carried out in the Kruzhyky site, which is situated in the East Carpathian Foreland, in the Dniester River valley, on the terrace 5 composed of the Mesopleistocene fluvial, glacigenic and aeolian deposits (Figs 1 and 2). These deposits are exposed along the section about 150 m long of the 15-17-metre-high river bank. In the undercutting of the Dniester River high bank the following five deposit complexes were described (Figs 3 and 4): 1. Fluvial complex-gravelly-sandy fining-up sequence. The Carpathian gravels with massive structure or faint horizontal stratification are covered by gravelly sands and sands with trough cross-stratification. They are overlain by sands and silts with ripple lamination merging into flaser lamination. These sediments were deposited as a result of rapid fall of flood in gravel-bed braided river. Gravel fractions represent deposition in longitudinal bars during high-energy flood flows, and sandy-gravelly and sandy-silty fractions-in channels between bars during waning flow (in the lower flow regime), at low river stages. 2. Fluvial-flood complex-package of alternating deformed clays with massive structure or faint lamination and silts with horizontal lamination. A lens, separated by erosion surface, occurs laterally. It is mostly composed of non-carbonate clays with numerous plant macroremnants, strongly gleyed, with interbeddings of sand. The silty-clayey complex was deposited from suspension, most probably after floods in depressions on floodplain. The lens of organogenic material (Fig. 5, Tables 3 and 4) is probably the result of deposition in cut off shallow channel (a kind of muddy depression) with periodically active weak flow. Based on the palaeobiological (pollen, macroremnants, Ostracoda) analyses of the deposits filling the reservoir, we find that it existed in cold climate and was surrounded with scarce sedge vegetation. 3. Proglacial complex-sandy-silty rhythmite composed

Aeolian Desertification and its Control in Northern of China

NASA Astrophysics Data System (ADS)

Wang, Tao

2017-04-01

Aeolian desertification is land degradation through wind erosion mainly resulted from the excessive human activities in arid, semiarid and part of sub-humid regions in Northern China. To compare the analyses results of remote sensing data in late of 1950, 1975, 1987, 2000 and 2010, we can summarize that the development of aeolian desertified land in Northern China had being accelerated for 5 decades, as its annual expanded rate was 1,560 km2 during late of 1950 and 1975, 2,100 km2 between 1975 and 1988, 3,600 km2 from 1988 to 2000 and -1375 km2 from 2000 to 2010. The whole situation of desertification comes to be depraved before 2000 and to be improve after 2000. The human impact is much more active than natural one on the process of aeolian desertification which mainly incarnates on the changes of the landuse fashion (from rangeland to farmland) and enhance of landuse intensity (over-cultivation, over-grassing and over-fuelwood collection). The natural vegetation had been destroyed by the human activities that had accelerated to the development or/and control of aeolian desertification. China has made much progresses in understanding and combating aeolian desertification through many efforts for decades and there were many projects have been carried out. One of among them is the National Project of Grain for Green Program and more than 1000 counties in 22 provinces have been included into this project. The objective is to withdraw 3.67 million ha of dry land farming and degraded steppe, and 5.13 million ha of aeolian desertified land suited to reforestation and revegetation will be rehabilitated. There are about 8 million ha of lands under the threats of aeolian desertified land will be brought under control in the next ten years and 26.67 million ha of windbreaks will be planted. The total financial input is estimated to 75 billion Yuan (11 billion US) what is entirely from the central government.

A study of global sand seas

USGS Publications Warehouse

McKee, Edwin D.

1979-01-01

The birth of the idea that led to this publication on "Global Sand Seas" dates back to the late 1920's. At that time I was engaged in a study of the Coconino Sandstone of Arizona's Grand Canyon. Considerable controversy existed then as to whether this sandstone was a subaqueous deposit or was composed of wind-formed dunes. It became apparent that definitive literature was sparse or lacking on types of dunes, global distribution of these types, the mechanics of their development, the precise nature of their internal structure of cross-stratificiation, and the relation of wind systems to these sand forms. Especially lacking were data on criteria that could confidently be used in the recognition of ancient dunes. The common denominator in this publication is eolian sand bodies. Although the book is concerned primarily with desert sand seas, the subject matter is not restricted to deserts; it includes many references to deposits of coastal sand and to sand bodies in humid climates. Nor does the book deal exclusively with dunes, which, according to most definitions, involve mounds or hills. Many references are made to sand sheets, sand stringers, and other types of sand deposits that have no prominent topographic expression. All sand bodies accumulated by the action of wind are discussed. Chapters A-J of this publication are primarily topical. Chapters cover the grain texture, the color, and the structure of modern dunes and other eolian sands. Special treatment is given to the relation of wind data to dune interpretation, the evolution of form in current-deposited sand bodies as determined from experimental studies, and the discriminant analysis technique for differentiating between coastal and inland desert sands. This topical part of the publication also includes an analysis of criteria used in ancient deposits to interpret their eolian genesis and a consideration of economic application of the principles described, including a discussion of potentials and problems

Transport of colloidal silica in unsaturated sand: Effect of charging properties of sand and silica particles.

PubMed

Fujita, Yosuke; Kobayashi, Motoyoshi

2016-07-01

We have studied the transport of colloidal silica in various degrees of a water-saturated Toyoura sand column, because silica particles are widely used as catalyst carriers and abrasive agents, and their toxicity is reported recently. Since water-silica, water-sand, and air-water interfaces have pH-dependent negative charges, the magnitude of surface charge was controlled by changing the solution pH. The results show that, at high pH conditions (pH 7.4), the deposition of colloidal silica to the sand surface is interrupted and the silica concentration at the column outlet immediately reaches the input concentration in saturated conditions. In addition, the relative concentration of silica at the column outlet only slightly decreases to 0.9 with decreasing degrees of water saturation to 38%, because silica particles are trapped in straining regions in the soil pore and air-water interface. On the other hand, at pH 5 conditions (low pH), where sand and colloid have less charge, reduced repulsive forces result in colloidal silica attaching onto the sand in saturated conditions. The deposition amount of silica particles remarkably increases with decreasing degrees of water saturation to 37%, which is explained by more particles being retained in the sand column associated with the air-water interface. In conclusion, at higher pH, the mobility of silica particles is high, and the air-water interface is inactive for the deposition of silica. On the other hand, at low pH, the deposition amount increases with decreasing water saturation, and the particle transport is inhibited. Copyright © 2016 Elsevier Ltd. All rights reserved.

An Introduction to Using Surface Geophysics to Characterize Sand and Gravel Deposits

USGS Publications Warehouse

Lucius, Jeffrey E.; Langer, William H.; Ellefsen, Karl J.

2006-01-01

This report is an introduction to surface geophysical techniques that aggregate producers can use to characterize known deposits of sand and gravel. Five well-established and well-tested geophysical methods are presented: seismic refraction and reflection, resistivity, ground penetrating radar, time-domain electromagnetism, and frequency-domain electromagnetism. Depending on site conditions and the selected method(s), geophysical surveys can provide information concerning aerial extent and thickness of the deposit, thickness of overburden, depth to the water table, critical geologic contacts, and location and correlation of geologic features. In addition, geophysical surveys can be conducted prior to intensive drilling to help locate auger or drill holes, reduce the number of drill holes required, calculate stripping ratios to help manage mining costs, and provide continuity between sampling sites to upgrade the confidence of reserve calculations from probable reserves to proved reserves. Perhaps the greatest value of geophysics to aggregate producers may be the speed of data acquisition, reduced overall costs, and improved subsurface characterization.

An Introduction to Using Surface Geophysics to Characterize Sand and Gravel Deposits

USGS Publications Warehouse

Lucius, Jeffrey E.; Langer, William H.; Ellefsen, Karl J.

2007-01-01

This report is an introduction to surface geophysical techniques that aggregate producers can use to characterize known deposits of sand and gravel. Five well-established and well-tested geophysical methods are presented: seismic refraction and reflection, resistivity, ground penetrating radar, time-domain electromagnetism, and frequency-domain electromagnetism. Depending on site conditions and the selected method(s), geophysical surveys can provide information concerning areal extent and thickness of the deposit, thickness of overburden, depth to the water table, critical geologic contacts, and location and correlation of geologic features. In addition, geophysical surveys can be conducted prior to intensive drilling to help locate auger or drill holes, reduce the number of drill holes required, calculate stripping ratios to help manage mining costs, and provide continuity between sampling sites to upgrade the confidence of reserve calculations from probable reserves to proved reserves. Perhaps the greatest value of geophysics to aggregate producers may be the speed of data acquisition, reduced overall costs, and improved subsurface characterization.

Wind-blown sand on beaches: an evaluation of models

NASA Astrophysics Data System (ADS)

Sherman, Douglas J.; Jackson, Derek W. T.; Namikas, Steven L.; Wang, Jinkang

1998-03-01

Five models for predicting rates of aeolian sand transport were evaluated using empirical data obtained from field experiments conducted in April, 1994 at a beach on Inch Spit, Co. Kerry, Republic of Ireland. Measurements were made of vertical wind profiles (to derive shear velocity estimates), beach slope, and rates of sand transport. Sediment samples were taken to assess characteristics of grain size and surface moisture content. Estimates of threshold shear velocity were derived using grain size data. After parsing the field data on the basis of the quality of shear velocity estimation and the occurrence of blowing sand, 51 data sets describing rates of sand transport and environmental conditions were retained. Mean grain diameter was 0.17 mm. Surface slopes ranged from 0.02 on the foreshore to about 0.11 near the dune toe. Mean shear velocities ranged from 0.23 m s -1 (just above the observed transport threshold) to 0.65 m s -1. Rates of transport ranged from 0.02 kg m -1 h -1 to more than 80 kg m -1 h -1. These data were used as input to the models of Bagnold [Bagnold, R.A., 1936. The Movement of Desert Sand. Proc. R. Soc. London, A157, 594-620], Kawamura [Kawamura, R., 1951. Study of Sand Movement by Wind. Translated (1965) as University of California Hydraulics Engineering Laboratory Report HEL 2-8, Berkeley], Zingg [Zingg, A.W., 1953. Wind tunnel studies of the movement of sedimentary material. Proc. 5th Hydraulics Conf. Bull. 34, Iowa City, Inst. of Hydraulics, pp. 111-135], Kadib [Kadib, A.A., 1965. A function for sand movement by wind. University of California Hydraulics Engineering Laboratory Report HEL 2-8, Berkeley], and Lettau and Lettau [Lettau, K. and Lettau, H., 1977. Experimental and Micrometeorological Field Studies of Dune Migration. In: K. Lettau and H. Lettau (Eds.), Exploring the World's Driest Climate. University of Wisconsin-Madison, IES Report 101, pp. 110-147]. Correction factors to adjust predictions of the rate of transport to account

Dust storms on Mars: Considerations and simulations

NASA Technical Reports Server (NTRS)

Greeley, R.; White, B. R.; Pollack, J. B.; Iverson, J. D.; Leach, R. N.

1977-01-01

Aeolian processes are important in modifying the surface of Mars at present, and appear to have been significant in the geological past. Aeolian activity includes local and global dust storms, the formation of erosional features such as yardangs and depositional features such as sand dunes, and the erosion of rock and soil. As a means of understanding aeolian processes on Mars, an investigation is in progress that includes laboratory simulations, field studies of earth analogs, and interpretation of spacecraft data. This report describes the Martian Surface Wind Tunnel, an experimental facility established at NASA-Ames Research Center, and presents some results of the general investigation. Experiments dealing with wind speeds and other conditions required for the initiation of particle movement on Mars are described and considerations are given to the resulting effectiveness of aeolian erosion.

The potential use of tar sand bitumen as paving asphalt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petersen, J.C.

1988-01-01

In this paper several research reports describing the preparation of potential paving asphalts from tar sand bitumen are reviewed and the results of the studies compared. The tar sand asphalts described in the studies were prepared from 1) hot water-recovered bitumen from deposits near San Luis Obispo, California (Edna deposits), and deposits near Vernal and Sunnyside, Utah; and 2) bitumen recovered from the Northwest Asphalt Ridge deposits near Vernal, Utah, by both in situ steamflood and in situ combustion recovery processes. Important properties of the tar sand asphalts compare favorably with those of specification petroleum asphalts. Laboratory data suggest thatmore » some tar sand asphalts may have superior aging characteristics and produce more water-resistant paving mixtures than typical petroleum asphalts.« less

Geographical Detector-Based Identification of the Impact of Major Determinants on Aeolian Desertification Risk

PubMed Central

Du, Ziqiang; Xu, Xiaoming; Zhang, Hong; Wu, Zhitao; Liu, Yong

2016-01-01

Arid and semi-arid areas in North China are facing the challenge of a rising aeolian desertification risk (ADR) due to the intertwined effects of complex natural processes and intensified anthropogenic activities. An accurate quantitative assessment of the relationship between ADR and its determinants is beneficial for understanding the driving mechanisms of aeolian desertification and for controlling future desertification. Previous studies have failed to quantify the relative role of determinants driving ADR and have been limited in assessing their interactive impacts. In this study, a spatial variance analysis-based geographical detector methodology is used to quantify the effects of geological, physical, and human factors on the occurrence of ADR in an area characterized by mountains and hills in northern China. It is found that soil type, precipitation, and wind velocity are the major determinants of ADR, which implies that geological and physical elements (e.g., soil attribute) and climatic factors (e.g., precipitation and wind velocity) rather than human activities have played a greater role in the incidence of ADR. Particularly, the results show that the interaction of various determinants causes significant non-linearly enhanced impacts on the ADR. The findings of our study will assist local inhabitants and policy makers in developing measures for wind prevention and sand control to mitigate the effects of desertification in the region. PMID:26987114

Geographical Detector-Based Identification of the Impact of Major Determinants on Aeolian Desertification Risk.

PubMed

Du, Ziqiang; Xu, Xiaoming; Zhang, Hong; Wu, Zhitao; Liu, Yong

2016-01-01

Arid and semi-arid areas in North China are facing the challenge of a rising aeolian desertification risk (ADR) due to the intertwined effects of complex natural processes and intensified anthropogenic activities. An accurate quantitative assessment of the relationship between ADR and its determinants is beneficial for understanding the driving mechanisms of aeolian desertification and for controlling future desertification. Previous studies have failed to quantify the relative role of determinants driving ADR and have been limited in assessing their interactive impacts. In this study, a spatial variance analysis-based geographical detector methodology is used to quantify the effects of geological, physical, and human factors on the occurrence of ADR in an area characterized by mountains and hills in northern China. It is found that soil type, precipitation, and wind velocity are the major determinants of ADR, which implies that geological and physical elements (e.g., soil attribute) and climatic factors (e.g., precipitation and wind velocity) rather than human activities have played a greater role in the incidence of ADR. Particularly, the results show that the interaction of various determinants causes significant non-linearly enhanced impacts on the ADR. The findings of our study will assist local inhabitants and policy makers in developing measures for wind prevention and sand control to mitigate the effects of desertification in the region.

Supply-limited horizontal sand drift at an ephemerally crusted, unvegetated saline playa

USGS Publications Warehouse

Gillette, Dale A.; Niemeyer, T.C.; Helm, P.J.

2001-01-01

A site at Owens Dry Lake was observed for more than 4 years. The site was a vegetation-free saline playa where the surface formed "ephemeral crusts," crusts that form after rainfall. Sometimes these crusts were destroyed and often a layer of particles on the crust would engage in vigorous aeolian activity. Three "phases" of active sand drifting are defined as almost no movement (extreme supply limitation), loose particles on crust with some degree of sand drift (moderate supply limitation), and unlimited source movement corresponding to a destroyed surface crust (unlimited supply). These "phases" occurred 45, 49, and 6% of the time, respectively. The accumulation of loose particles on the crust was mostly the result of in situ formation. Crusted sediments with loose particles on top can exhibit mass flux rates about the same as for noncrusted sediments. Crusted sediments limit or eliminate sand drift in two conditions: for rough crusts that effect a sufficiently high threshold friction velocity (above the wind friction velocity) and for limited amounts of loose particles on the crust where particle supply is less than would be transported in normal saltation for a thick sandy surface. These "supply-limited" cases are similar to wind erosion of limited spilled material on a hard concrete surface. We quantified "supply limitation" by defining a "potential" or "supply unlimited" sand drift function Q = AG where A represents supply limitation that decreases as the particle source is depleted. Here Q is the mass of sand transported through a surface perpendicular to the ground and to the wind and having unit width during time period t, and G = ??? u*(u*2 - u*t2) dt for u* > u*t. G is integrated for the same time period t as for Q, u* is the friction velocity of the wind, and u*t is the threshold friction velocity of the wind. Hard crusts (usually formed in the summer) tended to show almost no change of threshold friction velocity with time and often gave total

The Contribution of Oil Sands Industry Related Atmospheric THg and MeHg Deposition to Rivers of the Athabasca Oil Sands Region of Canada

NASA Astrophysics Data System (ADS)

Wasiuta, V. L.; Cooke, C. A.; Kirk, J.; Chambers, P. A.; Alexander, A. C.; Rooney, R. C.

2017-12-01

Rapid development of Oil Sands deposits in northern Alberta (Canada) raises concerns about human health and environmental impacts. We present results from a three-year study of winter-time atmospheric deposition of total mercury (THg) and methylmercury (MeHg) in six tributary watersheds of the Athabasca River. Seasonal snowpack THg and MeHg concentrations were obtained from spring-time sampling throughout the oil sands region. Winter-time Hg loads were then modeled at watershed and sub-basin scales using ArcGIS geostatistical kriging. To determine the potential impacts of snowmelt on aquatic ecosystems, six rivers were sampled at high frequency over 2012 to 2014 ice-free seasons. Hydrologic year (HY) and first discharge peak loads were then calculated from linear extrapolation of measured concentrations and mean daily discharge. Results showed high THg and MeHg loads from atmospheric deposition around regional upgrading facilities with loads diminishing outwards. This reflects the large proportion of particle bound Hg with a short atmospheric residence time, and deposition close to emission sources. Snowpacks within the six watersheds contained substantial proportions of tributary river THg and MeHg loads. For example, HY2014 snowpacks contained 24 to 46 % of river MeHg loads. All rivers showed a large proportion of HY loads discharged, within a few weeks, in the spring first discharge peak. HY2014 snowpack MeHg loads were greater than river loads in the first discharge peak for all watersheds except the High Hills. This first discharge peak is important as it occurs during critical growth periods for aquatic life. Large differences in tributary river THg and MeHg loads suggest factors other than atmospheric deposition and watershed scale contributed to the load. Considerably higher THg and MeHg snowpack loads in the Muskeg Watershed relative to river export suggest substantial losses to catchment soils or wetlands during snowmelt. Evaluation of factors that could

Compositional variations in sands of the Bagnold Dunes, Gale Crater, Mars, from visible-shortwave infrared spectroscopy and comparison with ground truth from the Curiosity Rover

USGS Publications Warehouse

Lapotre, Mathieu G.A.; Ehlmann, B. L.; Minson, Sarah E.; Arvidson, R. E.; Ayoub, F.; Fraeman, A. A.; Ewing, R. C.; Bridges, N. T.

2017-01-01

During its ascent up Mount Sharp, the Mars Science Laboratory Curiosity rover traversed the Bagnold Dune Field. We model sand modal mineralogy and grain size at four locations near the rover traverse, using orbital shortwave infrared single scattering albedo spectra and a Markov-Chain Monte Carlo implementation of Hapke's radiative transfer theory to fully constrain uncertainties and permitted solutions. These predictions, evaluated against in situ measurements at one site from the Curiosity rover, show that XRD-measured mineralogy of the basaltic sands is within the 95% confidence interval of model predictions. However, predictions are relatively insensitive to grain size and are non-unique, especially when modeling the composition of minerals with solid solutions. We find an overall basaltic mineralogy and show subtle spatial variations in composition in and around the Bagnold dunes, consistent with a mafic enrichment of sands with cumulative transport distance by sorting of olivine, pyroxene, and plagioclase grains during aeolian saltation. Furthermore, the large variations in Fe and Mg abundances (~20 wt%) at the Bagnold Dunes suggest that compositional variability induced by wind sorting may be enhanced by local mixing with proximal sand sources. Our estimates demonstrate a method for orbital quantification of composition with rigorous uncertainty determination and provide key constraints for interpreting in situ measurements of compositional variability within martian aeolian sandstones.

Evaluating process origins of sand-dominated fluvial stratigraphy

NASA Astrophysics Data System (ADS)

Chamberlin, E.; Hajek, E. A.

2015-12-01

Sand-dominated fluvial stratigraphy is often interpreted as indicating times of relatively slow subsidence because of the assumption that fine sediment (silt and clay) is reworked or bypassed during periods of low accommodation. However, sand-dominated successions may instead represent proximal, coarse-grained reaches of paleo-river basins and/or fluvial systems with a sandy sediment supply. Differentiating between these cases is critical for accurately interpreting mass-extraction profiles, basin-subsidence rates, and paleo-river avulsion and migration behavior from ancient fluvial deposits. We explore the degree to which sand-rich accumulations reflect supply-driven progradation or accommodation-limited reworking, by re-evaluating the Castlegate Sandstone (Utah, USA) and the upper Williams Fork Formation (Colorado, USA) - two Upper Cretaceous sandy fluvial deposits previously interpreted as having formed during periods of relatively low accommodation. Both units comprise amalgamated channel and bar deposits with minor intra-channel and overbank mudstones. To constrain relative reworking, we quantify the preservation of bar deposits in each unit using detailed facies and channel-deposit mapping, and compare bar-deposit preservation to expected preservation statistics generated with object-based models spanning a range of boundary conditions. To estimate the grain-size distribution of paleo-sediment input, we leverage results of experimental work that shows both bed-material deposits and accumulations on the downstream side of bars ("interbar fines") sample suspended and wash loads of active flows. We measure grain-size distributions of bar deposits and interbar fines to reconstruct the relative sandiness of paleo-sediment supplies for both systems. By using these novel approaches to test whether sand-rich fluvial deposits reflect river systems with accommodation-limited reworking and/or particularly sand-rich sediment loads, we can gain insight into large

Responses of aeolian desertification to a range of climate scenarios in China

NASA Astrophysics Data System (ADS)

Wang, Xunming; Hua, Ting; Ma, Wenyong

2016-06-01

Aeolian desertification plays an important role in earth-system processes and ecosystems, and has the potential to greatly impact global food production. The occurrence of aeolian desertification has traditionally been attributed to increases in wind speed and temperature and decreases in rainfall. In this study, by integrating the aeolian desertification monitoring data and climate and vegetation indices, we found that although aeolian desertification is influenced by complex climate patterns and human activities, increases in rainfall and temperature and decreases in wind speed may not be the key factors of aeolian desertification controls in some regions of China. Our results show that, even when modern technical approaches are used, different approaches to desertification need to be applied to account for regional differences. These results have important implications for future policy decisions on how best to combat desertification.

Investigations on Local Quartz Sand for Application in Glass Industry

NASA Astrophysics Data System (ADS)

Dararutana, Pisutti; Chetanachan, Prukswan; Wathanakul, Pornsawat; Sirikulrat, Narin

2009-03-01

Silica or glass sand is a special type of quartz sand that is suitable for glass-making, because of its high silica content, and its low content of iron oxide and other compounds. In Thailand, deposits of quartz sand are found as the beach and the river sands in many areas; eastern, southern, northeastern and northern. In this work, grain-size distribution and chemical analyses were carried out on 10 sand samples taken from various localities in Thailand such as Chanthaburi, Trat, Rayong, Chumphon, Nakhon Si, Pattani, Phuket, Songkhla, Nong Khai, and Tak provinces. The geological resources show that most of them are the surface-to-near-surface glass sand deposits. The sand grains in most deposits were mainly angular-to-rounded, except in some areas of either angular or rounded grains. Chemical analysis showed that the sands contained more than 95wt% silica and low content of Fe, Al, Ca, Mg, Na, and K. The concentration levels of these components in the samples confirm with internationally acceptable standard for glass production. The quartz sand dressing plants that used the spiral classifier to improve the properties of the quartz sands to meet the standard specifications are mostly located in the eastern area. It can be concluded that most of the quartz sand deposits in Thailand investigated show well-sorted grain-size with considerable purity, i.e. high-grade quality. The advanced works resulted in that these raw quartz sands can be used as raw material for fabrication of soda-lime, lead crystal, and lead-free high refractive index glasses. The colorless and various colored glass products have been satisfactorily used in the domestic art and glass manufactures.

Altitude of the top of the Sparta Sand and Memphis Sand in three areas of Arkansas

USGS Publications Warehouse

Pugh, Aaron L.; Westerfield, Paul W.; Gonthier, Gerard; Poynter, David T.

1998-01-01

The Sparta Sand and Memphis Sand form the second most productive aquifer in Arkansas. The Sparta Sand and Memphis Sand range in thick- ness from 0 to 900 feet, consisting of fine- to medium-grained sands interbedded with layers of silt, clay, shale, and minor amounts of lignite. Within the three areas of interest, the top surface of the Sparta Sand and Memphis Sand dips regionally east and southeast towards the axis of the Mississippi Embayment syncline and Desha Basin. Local variations in the top surface may be attributed to a combination of continued development of structural features, differential compaction, localized faulting, and erosion of the surface prior to subsequent inundation and deposition of younger sediments.

Holocene depositional environments and surface-level changes at Lake Fryxell, Antarctica

USGS Publications Warehouse

Whittaker, T.E.; Hall, B.L.; Hendy, C.H.; Spaulding, S.A.

2008-01-01

We report on Holocene surface-level variations of Lake Fryxell, Antarctica, as determined from multi-proxy analyses of 18 sediment cores. During this time accumulating sediments were predominantly aeolian sand with algal and carbonate laminae. Based on stratigraphy, mineralogy and diatom assemblages we suggest some carbonate laminae were deposited when lake level dropped, leading to concentration and subsequent precipitation of salts. Although lake level appears to have remained relatively stable throughout the Holocene, minor (<4.5 m below present) lowstands occurred at approximately 6400, 4700, 3800 and ??? 1600 cal. yr BP. The stability of Lake Fryxell during the Holocene contrasts with large-scale variability at other Dry Valleys lakes (eg, Lake Vanda) and with suggestions from chemical diffusion models of a near-desiccation at ???1200 cal. yr BP. The reason for the comparative stability of Lake Fryxell is uncertain, but may be the result of basin morphology and the number, aspect and proximity of meltwater sources. ?? 2008 SAGE Publications.

Aeolian dune sediment flux heterogeneity in Meridiani Planum, Mars.

PubMed

Chojnacki, Matthew; Urso, Anna; Fenton, Lori K; Michaels, Timothy I

2017-06-01

It is now known unambiguously that wind-driven bedform activity is occurring on the surface of Mars today, including early detections of active sand dunes in Meridiani Planum's Endeavour crater. Many of these reports are only based on a few sets of observations of relatively isolated bedforms and lack regional context. Here, we investigate aeolian activity across central Meridiani Planum and test the hypothesis that dune sites surrounding Endeavour crater are also active and part of region-wide sediment migration driven by northwesterly winds. All 13 dune fields investigated clearly showed evidence for activity and the majority exhibited dune migration (average rates of 0.6 m/Earth-year). Observations indicate substantial geographic and temporal heterogeneity of dune crest fluxes across the area and per site. Locations with multiple time steps indicate dune sand fluxes can vary by a factor of five, providing evidence for short periods of rapid migration followed by near-stagnation. In contrast, measurements at other sites are nearly identical, indicating that some dunes are in a steady-state as they migrate. The observed sediment transport direction was consistent with a regional northeasterly-to-northwesterly wind regime, revealing more variations than were appreciated from earlier, more localized studies. Craters containing shallow, degraded, flat-floored interiors tended to have dunes with high sediment fluxes/activity, whereas local kilometer-scale topographic obstructions (e.g., central peaks, yardangs) were found to be inversely correlated with dune mobility. Finally, the previous, more limited detections of dune activity in Endeavour crater have been shown to be representative of a broader, region-wide pattern of dune motion.

Geologic and paleoecologic studies of the Nebraska Sand Hills

USGS Publications Warehouse

Ahlbrandt, Thomas S.; Fryberger, S.G.; Hanley, John H.; Bradbury, J. Platt

1980-01-01

PART A: The Nebraska Sand Hills are an inactive, late Quaternary, most probably Holocene, dune field (covering 57,000 km 2 ) that have been eroded along streams and in blowouts, resulting in excellent lateral and vertical exposures of the stratification of dune and interdune sediments. This paper presents new data on the geometry, primary sedimentary structures, modification of sedimentary structures, direction of sand movement, and petrography of these eolian deposits. Eolian deposits of the Sand Hills occur as relatively thin (9-24 m) 'blanket' sands, composed of a complex of dune and discontinuous, diachronous interdune deposits unconformably overlying fluviolacustrine sediments. The internal stratification of large dunes in the Sand Hills (as high as 100 m), is similar to the internal stratification of smaller dunes of the same type in the Sand Hills, differing only in scale. Studies of laminae orientation in the Sand Hills indicate that transverse, barchan, and blowout dunes can be differentiated in rocks of eolian origin using both the mean dip angle of laminae and the mean angular deviation of dip direction. A variety of secondary structures modify or replace primary eolian stratification in the Sand Hills, the more common of which are dissipation structures and bioturbation. Dissipation structures in the Sand Hills may develop when infiltrating water deposits clay adjacent to less permeable layers in the sand, or along the upper margins of frozen layers that form in the sands during winter. Cross-bed measurements from dunes of the Nebraska Sand Hills necessitate a new interpretation of the past sand transport directions. The data from these measurements indicate a general northwest-to-southeast drift of sand, with a more southerly drift in the southeast part of the Sand Hills. A large area of small dunes < 100 m high) described by Smith (1965) as linear or seif in the central part of the Sand Hills was interpreted by him on the basis of morphology only. We

Constraints on Paleotsunami Runup Derived from Sand Deposits Mantling Three Holocene Marine Terraces at Puatai Beach, Northern Hikurangi Subduction Margin, New Zealand

NASA Astrophysics Data System (ADS)

Clark, K.; Litchfield, N. J.; Cochran, U. A.; Berryman, K. R.; Power, W. L.; Steele, R.

2016-12-01

At Puatai Beach, Gisborne, New Zealand, a 90-m-long continuous trench was excavated across a sequence of three marine terraces. The trench exposed the stratigraphy of deposits mantling the stepped shore platforms. The sequence of shelly sand and gravel beach deposits and silty colluvium allowed us to reconstruct the timing of earthquakes that uplifted the terraces, and place constraints on the age, runup and inundation distances of tsunamis that impacted the coastline in the late Holocene. Radiocarbon ages from shelly beach deposits lying on the platforms were used to date the terrace uplift ages at 1920-1650 (upper), 1270-1030 (middle), and 520-320 (lower) cal. yr BP respectively; we interpret these ages as the timing of large (M7+) paleoearthquakes on the nearshore Gable End Fault. With the inner edge of the highest shore platform reaching 9 m elevation, this flight of terraces has an average uplift rate of 5.6 ± 1 mm/yr, the highest uplift rate along the Hikurangi margin. The silty colluvium layers overlying the beach deposits contain thin semi-continuous sand layers. Based on chronological, geomorphological, sedimentological and biological considerations we suggest that at least some of these sand layers are tsunami deposits. Three sand layers were dated at 1190-930, 400-100, and 450-150 cal. yr BP, and the chronological overlap of the latter two suggests they could be the same event. Estimates of tsunami run-up were obtained from the surveyed maximum heights, and allowing for terrace uplift, they were 9.3 ± 0.5 m, 12.6 ± 0.5 m and 4.2-1.2 ± 0.5 m amsl, for the two dated and one un-dated paleotsunamis respectively; inundation distances were 58 m, 61 m, and 23 m. The inferred tsunami ages are slightly younger than the time of uplift of the marine terraces, and this, as well as their stratigraphic position within colluvium, suggests they were not necessarily triggered by rupture of the Gable End Fault. The younger ages potentially overlap tsunami deposits

Primary sedimentary structures and the internal architecture of a Martian sand body in search of evidence for sand transport and deposition

NASA Technical Reports Server (NTRS)

Basu, Abhijit

1988-01-01

Lunar experiences show that unmanned sample return missions, despite limitations on sample size, can produce invaluable data to infer crustal processes, regolith processes, regolith-atmosphere/ionosphere interaction processes, etc. Drill cores provide a record of regolith evolution as well as a more complete sample of the regolith than small scoops and/or rakes. It is proposed that: (1) a hole be drilled in a sand body to obtain continuous oriented cores; a depth of about 10 m would be compatible with what we know of bed form hierarchy of terrestrial stream deposits; (2) two trenches, at right angles to each other and close to the drill-hole, be dug and the walls scraped lightly such that primary/internal sedimentary structures of the sand body become visible; (3) the walls of the trenches be made gravitationally stable by impregnation techniques; (4) acetate or other peels of a strip on each wall be taken; and (5) appropriately scaled photographs of the walls be taken at different sun-angles to ensure maximum ease of interpretation of sedimentary structures; and, to correlate these structural features with those in the core at different depth levels of the core.

A Process-Based Transport-Distance Model of Aeolian Transport

NASA Astrophysics Data System (ADS)

Naylor, A. K.; Okin, G.; Wainwright, J.; Parsons, A. J.

2017-12-01

We present a new approach to modeling aeolian transport based on transport distance. Particle fluxes are based on statistical probabilities of particle detachment and distributions of transport lengths, which are functions of particle size classes. A computational saltation model is used to simulate transport distances over a variety of sizes. These are fit to an exponential distribution, which has the advantages of computational economy, concordance with current field measurements, and a meaningful relationship to theoretical assumptions about mean and median particle transport distance. This novel approach includes particle-particle interactions, which are important for sustaining aeolian transport and dust emission. Results from this model are compared with results from both bulk- and particle-sized-specific transport equations as well as empirical wind tunnel studies. The transport-distance approach has been successfully used for hydraulic processes, and extending this methodology from hydraulic to aeolian transport opens up the possibility of modeling joint transport by wind and water using consistent physics. Particularly in nutrient-limited environments, modeling the joint action of aeolian and hydraulic transport is essential for understanding the spatial distribution of biomass across landscapes and how it responds to climatic variability and change.

The Variability of Transverse Aeolian Ripples in Troughs on Mars

NASA Technical Reports Server (NTRS)

Bourke, M. C.; Wilson, S.A.; Zimbelman, J. R.

2003-01-01

A precursory glance at MGS images of the surface of Mars show an abundance of aeolian transverse ridges. These ridges are located in a variety of geological terrains. Zimbelman and Wilson have separated the small-scale aeolian features of Syrtis Major into six categories: ripples associated with obstacles, ripple bands, ripple fields, ripple patches, isolated ripple patches and ripples associated with dunes. This paper focuses on one of these categories, that of ripple bands which tend to accumulate within linear troughs. As the origin of these features is still being studied (i.e. ripples versus dunes), we refer to them simply as transverse aeolian ridges.

Aeolian sediment transport on a beach: Surface moisture, wind fetch, and mean transport

NASA Astrophysics Data System (ADS)

Bauer, B. O.; Davidson-Arnott, R. G. D.; Hesp, P. A.; Namikas, S. L.; Ollerhead, J.; Walker, I. J.

2009-04-01

speed, unsteadiness, approach angle, flow compression, boundary layer development). Moisture content is widely acknowledged as an important factor in controlling release of sediment from the beach surface. All other things being equal, the rate of sediment transport over a wet surface is lesser than over a dry surface. On this beach, the moisture effect has two important influences: (a) in a temporal sense, the rate of sediment transport typically decreases in association with rainfall and increases when surface drying takes place; and (b) in a spatio-temporal sense, shoreline excursions associated with nearshore processes (such as wave run-up, storm surge, and tidal excursions) have the effect of constraining the fetch geometry of the beach—i.e., narrowing the width of the beach. Because saturated sand surfaces, such as found in the swash zone, will only reluctantly yield sediments to aeolian entrainment, the available beach surface across which aeolian transport can occur becomes narrower as the sea progressively inundates the beach. Under these constrained conditions, the transport system begins to shut down unless wind angle becomes highly oblique (thereby increasing fetch distance). In this study, maximum sediment transport was usually measured on the mid-beach rather than the upper beach (i.e., closer to the foredunes). This unusual finding is likely because of internal boundary layer development across the beach, which yields a decrease in near-surface wind speed (and hence, transport capacity) in the landward direction. Although widely recognized in the fluid mechanics literature, this decrease in near-surface shear stress as a by-product of a developing boundary layer in the downwind direction has not been adequately investigated in the context of coastal aeolian geomorphology.

Becquerel Crater Deposit

NASA Technical Reports Server (NTRS)

2002-01-01

(Released 28 May 2002) The finely layered deposit in Becquerel crater, seen in the center of this THEMIS image, is slowly being eroded away by the action of windblown sand. Dark sand from a source north of the bright deposit is collecting along its northern edge, forming impressive barchan style dunes. These vaguely boomerang-shaped dunes form with their two points extending in the downwind direction, demonstrating that the winds capable of moving sand grains come from the north. Grains that leave the dunes climb the eroding stair-stepped layers, collecting along the cliff faces before reaching the crest of the deposit. Once there, the sand grains are unimpeded and continue down the south side of the deposit without any significant accumulation until they fall off the steep cliffs of the southern margin. The boat-hull shaped mounds and ridges of bright material called yardangs form in response to the scouring action of the migrating sand. To the west, the deposit has thinned enough that the barchan dunes extend well into the deeply eroded north-south trending canyons. Sand that reaches the south side collects and reforms barchan dunes with the same orientation as those on the north side of the deposit. Note the abrupt transition between the bright material and the dark crater floor on the southern margin. Steep cliffs are present with no indication of rubble from the obvious erosion that produced them. The lack of debris at the base of the cliffs is evidence that the bright material is readily broken up into particles that can be transported away by the wind. The geological processes that are destroying the Becquerel crater deposit appear active today. But it is also possible that they are dormant, awaiting a particular set of climatic conditions that produces the right winds and perhaps even temperatures to allow the erosion to continue.

Implications of (reworked) aeolian sediments and paleosols for Holocene environmental change in Western Mongolia

NASA Astrophysics Data System (ADS)

Klinge, Michael; Lehmkuhl, Frank; Schulte, Philipp; Hülle, Daniela; Nottebaum, Veit

2017-09-01

In the semi-arid to semi-humid regions of western Mongolia four different geomorphological aeolian and fluvial archives were investigated in order to gain environmental information of landscape evolution during the late glacial and the Holocene. These archives, which contain aeolian deposits, fluvial sediments, and paleosols, are situated upon glacial moraines, fluvial terraces, floodplains, or mountain slopes. While radiometric dating provides information about the age of the sediment and paleosols, grain size and element distribution provide information about the sediment source and soil development. Extensive aeolian sediment transport occurred from 17 to 10 ka during the late glacial when climate was cold and dry. Since that period the developing steppe and alpine meadow vegetation served as a dust trap. During the warm and wet early to mid-Holocene sediment transport was reduced under a dense vegetation cover. All paleosols of the investigated archives show late Holocene ages which point to an environmental turning point around 3 ka. Since then, the Neoglacial period started with cooler climate conditions and periglacial processes intensified again. Recognizable glacier advances occurred during the Little Ice Age several centuries ago. Since then, global climate change leads to warmer and more arid conditions. During the late Holocene, a new period of strong geomorphological activity started and huge quantities of aeolian, colluvial and fluvial sediment accumulated. These intensified soil relocation processes cannot be explained exclusively by climate change because there are no explicit indications found in the palynological and lacustrine records of Mongolia. This discrepancy suggests that the additional factor of human impact has to be considered, which amplified the climate signal on the landscape. Simultaneously, when the enhanced geomorphological processes occurred, the prehistoric people changed from hunting and gathering to livestock husbandry. A first

Aeolian Abrasion at the Curiosity Landing Site: Clues to the Role of Wind in Landscape Modification

NASA Astrophysics Data System (ADS)

Bridges, N. T.; Le Mouélic, S.; Hallet, B.; Newman, C. E.; Rice, M. S.; Blaney, D. L.; Calef, F. J.; Herkenhoff, K. E.; Langevin, Y.; Lewis, K. W.; Maurice, S.; Pinet, P. C.; Wiens, R. C.; de Pablo, M.; Renno, N. O.

2013-12-01

The broad scale geomorphology of Gale Crater reflects diverse aeolian processes, from airfall settling that likely deposited much of the upper and some of the lower units of Mt. Sharp, to evidence of extensive wind exhumation and removal of material exterior to the mound, to active dunes on the crater floor. The integrated effect of aeolian sand transport can also be examined on a much smaller scale by the study of ventifacts, rocks that have been abraded by windborne particles. A diversity of ventifacts are found along Curiosity's traverse through the upper 'hummocky' (HY) geomorphic unit and the lower Yellowknife Bay (YKB) sedimentary rocks. The textures are analogous to abrasion features found on Earth and include cm-scale facets, keels, elongated pits, grooves, flutes, and basal sills. High-resolution images from ChemCam's Remote Micro-Imager also show mm-scale lineations. Evidence of differential erosion is common, with HY conglomerates (e.g., Hottah, Link) and the YKB Sheepbed mudstone unit containing distinct wind tails in the lee of resistant pebbles, and bedding features within Rocknest 3, the YKB Shaler sandstone unit, and other layered rocks displaying prominent ridge-groove topography. ChemCam LIBS depth profile data so far show no strong evidence for chemical differences in the elemental composition between abraded and non-abraded surfaces (as determined from qualitative assessment), as might be expected if there were rock coatings or weathering rinds undergoing active abrasion. Preliminary measurements of ventifact texture and wind tail orientations indicate sandblasting in HY and YKB from predominantly southwesterly and northerly directions, respectively. Based on meso-scale models of current winds and REMS results, SW flow is uncommon whereas N winds are frequent. Compositional and textural information from the suite of MSL instruments indicate that HY rocks are dominated by various types of basalt (either as whole rocks or the resistant clasts in

Sand pulses and sand patches on the Colorado River in Grand Canyon

USGS Publications Warehouse

Grams, Paul E.; Buscombe, Daniel; Topping, David; Mueller, Erich R.

2017-01-01

Alluvial sandbars occur in lateral recirculation zones (eddies) along the Colorado River in Grand Canyon National Park (Schmidt, 1990). Resource managers periodically release controlled floods from the upstream Glen Canyon Dam to rebuild these bars (Grams et al., 2015), which erode during fluctuating dam releases, and by hillslope runoff and wind deflation (Hazel et al., 2010). Because the dam blocks upstream sediment, episodic floods from tributaries provide the only supply to replace eroded sand; and much of this sand originates from a single tributary (Topping et al., 2000). Here, we present new evidence for the downstream translation of the sand component of these sediment inputs as discontinuous sand pulses. Improved understanding of the behaviour of these sand pulses may be used to adjust the timing, magnitude, and duration of controlled floods to maximize potential for deposition on sandbars in different segments of the 450 km-long Grand Canyon.

Numerical simulation of wind-sand movement in the reversed flow region of a sand dune with a bridge built downstream.

PubMed

He, Wei; Huang, Ning; Xu, Bin; Wang, Wenbo

2018-04-23

A bridge built inside the reversed flow region of a sand dune will change the characteristics of wind-sand movement in this region. The Reynolds-averaged Navier-Stokes simulation and discrete particle tracing are used to simulate the wind-sand movement around a sand dune with a bridge built inside the reversed region. Three cases with different bridge positions are studied. The results show that 1) compared with the isolated dune case, a tall bridge built at the leeward toe leads to an increase in the deposition rate on the leeward slope and a longer reversed flow region downstream of the sand dune; meanwhile, the high speed of crosswind on the bridge indicates that some measures should be taken to protect trains from strong crosswind; 2) a low bridge at the leeward toe has little effect on the sand deposition and reversed flow region of the dune; however, low sand transport rate and crosswind speed on the bridge show that anti-crosswind/sand measures should be taken according to the actual situation and 3) a low bridge on the leeward slope has little effect on the length of reversed flow region, however, high crosswind speed and sand flux on the bridge reveal the need of anti-crosswind/sand measures on the bridge. Moreover, the bridges in the reversed flow region increase the sand flux near the leeward crest; as a result, the moving patterns of the sand dune are changed.

Density-lag anomaly patterns in backshore sands along a paraglacial barrier spit

NASA Astrophysics Data System (ADS)

Pupienis, Donatas; Buynevich, Ilya; Jarmalavičius, Darius; Fedorovič, Julija; Žilinskas, Gintautas; Ryabchuk, Daria; Kovaleva, Olga; Sergeev, Alexander; Cichon-Pupienis, Anna

2016-04-01

The Curonian Spit, located along the southeast Baltic Sea coast, is one of the longest paraglacial mega-barriers in the world (~100 km) and is characteried by microtidal sandy beaches and unbroken foredune ridge emplaced by human activities in historical times. Both are dominated by quartzo-feldpathic sand, with various fractions of heavy minerals that may be concentrated as density lag. Such heavy-mineral concentrations (HMCs) may be distributed weither randomly or regularly along the coast, depending on the geological framework, hydro-aeolian processes, and human activities (e.g., steel elements of coastal engineering structures, military installations, etc.). In this study, we focus on the longshore patterns in HMC distribution and relative magnitude (mainly the concentration of ferrimagnetic components). Along the entire Curonian Spit coast (Russia-Lithuania), a total of 184 surface sand samples were collected at 1 km interval from the berm and foredune toe (seaward base). HMCs were characterized in the laboratory using bulk low-field magnetic susceptibility (MS). The Wavelength and Lomb spectral analysis were used to assess the spatial rhythmicity of their longshore distribution. Generally, quartz sand is characterised by low MS values of ĸ<50 μSI, whereas higher values ĸ>150 μSI are typical for heavy mineral-rich sand. MS values on the berm and foredune toe range from 11.2-4977.9 μSI and from 9.2-3153.0 μSI, respectively. Density lag anomalies had MS values exceeding an average value by ≥3 times. Wavelength and Lomb spectral analysis allowed to identify several clusters of periodicities with wavelength varying from 2-12 km, with power spectra having statistically significant values (>95 % CI). Along the modern Curonian Spit coast, two scales of rhythmic pattern variation are evident: macroscale (≤12 km) and mesoscale (2-3 km). The former can be attributed to localized expressions of geological framework (iron-rich components) and engineering

3D Airflow patterns over coastal foredunes: implications for aeolian sediment transport

NASA Astrophysics Data System (ADS)

Jackson, Derek W. T.; Cooper, Andrew G.; Baas, Andreas C. W.; Lynch, Kevin; Beyers, Meiring

2010-05-01

A fundamental criterion for the development of coastal sand dunes is usually highlighted as a significant onshore wind component of the local wind field. The presence of large sand dune systems on coasts where the predominant wind blows offshore is therefore difficult to explain and usually they are attributed to the past occurrence of onshore winds and, by implication, subsequent changes in climate. Recent studies have shown that offshore winds can be deflected or 'steered' by existing dunes so that their direction changes. This can occur to such an extent that a process known as 'flow reversal' can arise, whereby the initially offshore wind actually flows onshore at the beach. This process is important because it can cause sand to be blown from the beach and into the dunes, causing them to grow. This may be central in explaining the presence of extensive dunes on coasts where the dominant wind is offshore, but is also important in how dunes recover after periods of wave erosion during storms. Offshore winds have traditionally been excluded from sediment budget calculations for coastal dunes, but when they do transport sand onshore, this may have been an important oversight leading to significant underestimates of the volume of sand being transported by wind. This work investigates the controls on the processes and the mechanisms involved in deformation of the flow and resulting sediment transport at coastal foredunes in Northern Ireland. We use a combination of field measurement of wind and sediment transport coupled with state-of-the-art aerodynamic modelling using computational fluid dynamics (CFD) and 3-D sonic anemometry. Our working hypothesis is that offshore winds contribute substantially to foredune behaviour on leeside coasts. Preliminary results show strong reverse flow eddies in the seaward side of the foredunes during offshore wind events. These secondary flow reversals have been above velocity threshold and are transport capable. Using CFD modelling

A Comparative Analysis of Barchan Dunes in the Intra-Crater Dune Fields and the North Polar Sand Sea

NASA Technical Reports Server (NTRS)

Bourke, M. C.; Balme, M.; Zimbelman, J.

2004-01-01

Martian sand dunes have the potential to contribute data on geological history through a study of their form. Recognition of the characteristics of both recent and ancient dunes is the first step towards understanding the present as well as past aeolian systems, and by proxy, climatic conditions on Mars. Dunes studied in detail in Viking 1 and 2 Orbiter images have been classified as barchan, barchanoid, transverse, and complex. Regionally, they are concentrated in four locations: The North and South Polar regions, in intra crater dune fields and in troughs and valleys. Here we present the results of a morphometric analysis of barchan dunes in two of these locations: the North Polar Sand Sea (NPSS) and intra-crater dunes.

Plant Community and Nitrogen Deposition as Drivers of Alpha and Beta Diversities of Prokaryotes in Reconstructed Oil Sand Soils and Natural Boreal Forest Soils

PubMed Central

Prescott, Cindy E.; Renaut, Sébastien; Terrat, Yves; Grayston, Sue J.

2017-01-01

ABSTRACT The Athabasca oil sand deposit is one of the largest single oil deposits in the world. Following surface mining, companies are required to restore soil-like profiles that can support the previous land capabilities. The objective of this study was to assess whether the soil prokaryotic alpha diversity (α-diversity) and β-diversity in oil sand soils reconstructed 20 to 30 years previously and planted to one of three vegetation types (coniferous or deciduous trees and grassland) were similar to those found in natural boreal forest soils subject to wildfire disturbance. Prokaryotic α-diversity and β-diversity were assessed using massively parallel sequencing of 16S rRNA genes. The β-diversity, but not the α-diversity, differed between reconstructed and natural soils. Bacteria associated with an oligotrophic lifestyle were more abundant in natural forest soils, whereas bacteria associated with a copiotrophic lifestyle were more abundant in reconstructed soils. Ammonia-oxidizing archaea were most abundant in reconstructed soils planted with grasses. Plant species were the main factor influencing α-diversity in natural and in reconstructed soils. Nitrogen deposition, pH, and plant species were the main factors influencing the β-diversity of the prokaryotic communities in natural and reconstructed soils. The results highlight the importance of nitrogen deposition and aboveground-belowground relationships in shaping soil microbial communities in natural and reconstructed soils. IMPORTANCE Covering over 800 km2, land disturbed by the exploitation of the oil sands in Canada has to be restored. Here, we take advantage of the proximity between these reconstructed ecosystems and the boreal forest surrounding the oil sand mining area to study soil microbial community structure and processes in both natural and nonnatural environments. By identifying key characteristics shaping the structure of soil microbial communities, this study improved our understanding of

Aeolian dune sediment flux heterogeneity in Meridiani Planum, Mars

PubMed Central

Chojnacki, Matthew; Urso, Anna; Fenton, Lori K.; Michaels, Timothy I.

2018-01-01

It is now known unambiguously that wind-driven bedform activity is occurring on the surface of Mars today, including early detections of active sand dunes in Meridiani Planum’s Endeavour crater. Many of these reports are only based on a few sets of observations of relatively isolated bedforms and lack regional context. Here, we investigate aeolian activity across central Meridiani Planum and test the hypothesis that dune sites surrounding Endeavour crater are also active and part of region-wide sediment migration driven by northwesterly winds. All 13 dune fields investigated clearly showed evidence for activity and the majority exhibited dune migration (average rates of 0.6 m/Earth-year). Observations indicate substantial geographic and temporal heterogeneity of dune crest fluxes across the area and per site. Locations with multiple time steps indicate dune sand fluxes can vary by a factor of five, providing evidence for short periods of rapid migration followed by near-stagnation. In contrast, measurements at other sites are nearly identical, indicating that some dunes are in a steady-state as they migrate. The observed sediment transport direction was consistent with a regional northeasterly-to-northwesterly wind regime, revealing more variations than were appreciated from earlier, more localized studies. Craters containing shallow, degraded, flat-floored interiors tended to have dunes with high sediment fluxes/activity, whereas local kilometer-scale topographic obstructions (e.g., central peaks, yardangs) were found to be inversely correlated with dune mobility. Finally, the previous, more limited detections of dune activity in Endeavour crater have been shown to be representative of a broader, region-wide pattern of dune motion. PMID:29576818

Sand effects on thermal barrier coatings for gas turbine engines

NASA Astrophysics Data System (ADS)

Walock, Michael; Barnett, Blake; Ghoshal, Anindya; Murugan, Muthuvel; Swab, Jeffrey; Pepi, Marc; Hopkins, David; Gazonas, George; Kerner, Kevin

Accumulation and infiltration of molten/ semi-molten sand and subsequent formation of calcia-magnesia-alumina-silicate (CMAS) deposits in gas turbine engines continues to be a significant problem for aviation assets. This complex problem is compounded by the large variations in the composition, size, and topology of natural sands, gas generator turbine temperatures, thermal barrier coating properties, and the incoming particulate's momentum. In order to simplify the materials testing process, significant time and resources have been spent in the development of synthetic sand mixtures. However, there is debate whether these mixtures accurately mimic the damage observed in field-returned engines. With this study, we provide a direct comparison of CMAS deposits from both natural and synthetic sands. Using spray deposition techniques, 7% yttria-stabilized zirconia coatings are deposited onto bond-coated, Ni-superalloy discs. Each sample is coated with a sand slurry, either natural or synthetic, and exposed to a high temperature flame for 1 hour. Test samples are characterized before and after flame exposure. In addition, the test samples will be compared to field-returned equipment. This research was sponsored by the US Army Research Laboratory, and was accomplished under Cooperative Agreement # W911NF-12-2-0019.

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

USGS Publications Warehouse

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

2007-01-01

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

First direct observation of the link between supercritical flow processes, crescent-shape bedforms and massive sand deposits

NASA Astrophysics Data System (ADS)

Hage, Sophie; Cartigny, Matthieu; Clare, Michael; Sumner, Esther; Talling, Peter; Vendettuoli, Daniela; Hughes Clarke, John; Hubbard, Stephen

2017-04-01

Massive sandstones have been studied in many outcrops worldwide as they form a building stone of good subsurface petroleum reservoirs. Massive sands are often associated with turbidites sequences in ancient sedimentary successions. Turbidites are widely known to result from the deceleration of turbidity currents, these underwater flows driven by the excess density of sediments they carry in suspension. Depositional processes that are associated with the formation of massive sands are still under debate in the literature and many theoretical mechanisms have been suggested based on outcrops interpretations, lab experiments and numerical models. Here we present the first field observations that show how massive sands are generated from flow instabilities associated with supercritical flow processes occurring in turbidity currents. We combine turbidity current measurements with seafloor topography observations on the active Squamish Delta, British Columbia (Canada). We show that supercritical flow processes shape crescent-shape bedforms on the seafloor, and how these crescent-shape bedforms are built by massive sands. This modern process-product link is then used to interpret massive sandstone successions found in ancient outcrops. We demonstrate that supercritical-flow processes can be recognised in outcrops and that these processes produce highly diachronous stratigraphic surfaces in the rock record. This has profound implications on how to interpret ancient geological successions and the Earth history they archive.

Tephro- and chemo-stratigraphy of the Vulcanello Peninsula (Vulcano, Aeolian Islands)

NASA Astrophysics Data System (ADS)

Rosi, M.; Fusillo, R.; di Traglia, F.; Pistolesi, M.; Todman, A.; Menzies, M. A.

2009-12-01

New stratigraphic studies of the Vulcanello Peninsula have been used to better define the small-scale evolution of this young (1000 AD and 325±100 BP) volcanic center and to re-investigate the last 1000 years of volcanic history for the Island of Vulcano (Aeolian Islands, Southern Italy). Vulcanello Peninsula is the northern-most part of the Island of Vulcano. It comprises a shoshonitic lava platform and a volcanic edifice made up of three overlying cones, which are shoshonitic to trachytic in composition. Volcanic activity in this area was coeval with the recent eruptions of the La Fossa Cone, the present-day active center of the island. Our goal is to constrain the recent volcanic development of this mafic volcano and to focus on the historic eruptive activity of the two other recent or active centres in the southern Aeolian Islands, Mt. Pilato (Island of Lipari) and La Fossa Cone. In order to do so, we reconstructed the stratigraphical setting of the proximal deposits of the three Vulcanello cones, through the investigation of 25 outcrops. We analyzed the stratigraphy of the tephra blankets deposited on the lava platform, studying 10 trenches. Our intention is to integrate morphological, textural and chemical data in order to correlate these deposits with the Vulcanello, La Fossa Cone or Mt Pilato. LA-MC-ICPMS (RHUL) analysis of juvenile clasts is underway in order to investigate the evolution of the Vulcanello juvenile clasts. In addition 14C dating is planned on selected organic matter from the volcanostratigraphic sections. Our preliminary data for the Vulcanello proximal deposits suggest that each of the three cones experienced several eruptions, with a wide spectrum of eruptive styles and a diversity of chemistry. The oldest cone (Vulcanello I) is characterised by four different eruptions separated by minor unconformities or reworking material indicative of little or not time breaks in the eruptive cycle. The eruptions shift from Violent Strombolian to

Aeolian Processes at the Mars Exploration Rover Opportunity Landing Site

NASA Technical Reports Server (NTRS)

Sullivan, R.; Bell, J. F., III; Calvin, W.; Fike, D.; Golombek, M.; Greeley, R.; Grotzinger, J.; Herkenhoff, K.; Jerolmack, D.; Malin, M.

2005-01-01

The traverse of the Mars Exploration Rover Opportunity across its Meridiani Planum landing site has shown that wind has affected regolith by creating drifts, dunes, and ubiquitous ripples, by sorting grains during aeolian transport, by forming bright wind streaks downwind from craters seen from orbit, and by eroding rock with abrading, wind-blown material. Pre-landing orbiter observations showed bright and dark streaks tapering away from craters on the Meridiani plains. Further analysis of orbiter images shows that major dust storms can cause bright streak orientations in the area to alternate between NW and SE, implying bright wind streak materials encountered by Opportunity are transient, potentially mobilized deposits. Opportunity performed the first in situ investigation of a martian wind streak, focusing on a bright patch of material just outside the rim of Eagle crater. Data from Pancam, the Miniature Thermal Emission Spectrometer (Mini-TES), the Alpha-Particle X-Ray Spectrometer (APXS), and the Mossbauer spectrometer either are consistent with or permit an air fall dust interpretation. We conclude that air fall dust, deposited in the partial wind shadow of Eagle crater, is responsible for the bright streak seen from orbit, consistent with models involving patchy, discontinuous deposits of air fall dust distributed behind obstacles during periods of atmospheric thermal stability during major dust storms.

Evidence for Perchlorates and the Origin of Chlorinated Hydrocarbons Detected by SAM at the Rocknest Aeolian Deposit in Gale Crater

NASA Technical Reports Server (NTRS)

Glavin, Daniel P.; Freissinet, Caroline; Miller, Kristen E.; Eigenbrode, Jennifer L.; Brunner, Anna E.; Buch, Arnaud; Sutter, Brad; Archer, P. Douglas, Jr.; Atreya, Sushil K.; Brinckerhoff, William B.;

Landscape evolution on Mars - A model of aeolian denudation in Gale Crater

NASA Astrophysics Data System (ADS)

Day, M. D.; Kocurek, G.; Grotzinger, J. P.

2015-12-01

Aeolian erosion has been the dominant geomorphic agent to shape the surface of Mars for the past ~3.5 billion years. Although individual geomorphic features evidencing aeolian activity are well understood (e.g., yardangs, dune fields, and wind streaks), landscapes formed by aeolian erosion remain poorly characterized. Intra-crater sedimentary mounds are hypothesized to have formed by wind deflation of craters once filled with flat-lying strata, and, therefore, should be surrounded by landscapes formed by aeolian erosion. Here we present a landscape evolution model that provides both an initial characterization of aeolian landscapes, and a mechanism for large-scale excavation. Wind excavation of Gale Crater to form the 5 km high Mount Sharp would require removal of 6.4 x 104 km3 of sediment. Imagery in Gale Crater from satellites and the Mars Science Laboratory rover Curiosity shows a surface characterized by first-cycle aeolian erosion of bedrock. The overall landscape is interpreted to represent stages in a cycle of aeolian deflation and excavation, enhanced by physical weathering (e.g., thermal fracturing, cratering). Initial wind erosion of bedrock is enhanced along fractures, producing retreating scarps. Underlying less resistant layers then erode faster than the armoring cap rock, increasing relief in scarps to form retreating mesas. As scarp retreat continues, boulders from the armoring cap unit break away and cover the hillslopes of less resistant material below the scarps. Eventually all material from the capping unit is eroded away and a boulder-capped hill remains. Winnowing of fine material flattens hillslope topography, leaving behind a desert pavement. Over long enough time, this pavement is breached and the cycle begins anew. This cycle of landscape denudation by the wind is similar to that of water, but lacks characteristic subaqueous features such as dendritic drainage networks.

Measurement uncertainties in quantifying aeolian mass flux: evidence from wind tunnel and field site data

PubMed Central

Keijsers, Joep G.S.; Maroulis, Jerry; Visser, Saskia M.

2014-01-01

Aeolian sediment traps are widely used to estimate the total volume of wind-driven sediment transport, but also to study the vertical mass distribution of a saltating sand cloud. The reliability of sediment flux estimations from such measurements are dependent upon the specific configuration of the measurement compartments and the analysis approach used. In this study, we analyse the uncertainty of these measurements by investigating the vertical cumulative distribution and relative sediment flux derived from both wind tunnel and field studies. Vertical flux data was examined using existing data in combination with a newly acquired dataset; comprising meteorological data and sediment fluxes from six different events, using three customized catchers at Ameland beaches in northern Netherlands. Fast-temporal data collected in a wind tunnel shows that the median transport height has a scattered pattern between impact and fluid threshold, that increases linearly with shear velocities above the fluid threshold. For finer sediment, a larger proportion was transported closer to the surface compared to coarser sediment fractions. It was also shown that errors originating from the distribution of sampling compartments, specifically the location of the lowest sediment trap relative to the surface, can be identified using the relative sediment flux. In the field, surface conditions such as surface moisture, surface crusts or frozen surfaces have a more pronounced but localized effect than shear velocity. Uncertainty in aeolian mass flux estimates can be reduced by placing multiple compartments in closer proximity to the surface. PMID:25071984

Dust deposition and ambient PM10 concentration in northwest China: Spatial and temporal variability

USDA-ARS?s Scientific Manuscript database

Aeolian dust transport and deposition are important geophysical processes which influence global bio-geochemical cycles. Currently, reliable continental deposition data are scarce in central Asia. Located in the eastern part of central Asia, Xinjiang Province of northwestern China has long played a ...

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

USGS Publications Warehouse

Edgar, Lauren; Gupta, Sanjeev; Rubin, David M.; Lewis, Kevin W.; Kocurek, Gary A.; Anderson, Ryan; Bell, James F.; Dromart, Gilles; Edgett, Kenneth S.; Grotzinger, John P.; Hardgrove, Craig; Kah, Linda C.; LeVeille, Richard A.; Malin, Michael C.; Mangold, Nicholas; Milliken, Ralph E.; Minitti, Michelle; Palucis, Marisa C.; Rice, Melissa; Rowland, Scott K.; Schieber, Juergen; Stack, Kathryn M.; Sumner, Dawn Y.; Wiens, Roger C.; Williams, Rebecca M.E.; Williams, Amy J.

2018-01-01

This paper characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time, and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture, and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification to determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution, and bedform migration direction, this study concludes that the Shaler outcrop likely records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the northeast, across the surface of a bar that migrated southeast. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggests that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry, and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.

OSL age and stratigraphy of the Strauss sand sheet in New Mexico, USA

NASA Astrophysics Data System (ADS)

Hall, Stephen A.; Goble, Ronald J.

2015-07-01

The Strauss sand sheet occurs in south-central New Mexico, USA, and northern Chihuahua, Mexico, covering an area of about 4740 km2. Its chronology is determined by 19 OSL ages. The sand sheet formed primarily during three phases of eolian deflation and deposition, each phase with a separate sand source and under different climatic and environmental circumstances. The first phase of eolian sedimentation occurred 45 to 15 ka with the deposition of unit 1. The sand source for the first phase was beach-related features along the eastern shoreline of pluvial Lake Palomas in Mexico. The glacial-age climate was cool, wet, and windy because of the southern path of the jet stream at that time. After 15 ka, with the onset of warmer conditions of the Bølling-Allerød, the shutting down of the Palomas sand source, and wet conditions of the Younger Dryas, the sand sheet stabilized with weak soil development in unit 1. By 11 ka, the climate shifted to Holocene drying conditions and the second phase of sand accumulation began, forming unit 2; the sand source was the local deflation of the previously deposited unit 1 sand. The sand sheet stabilized again by 1.9 ka with slightly wetter late Holocene climate; a weak soil formed in unit 2 sand. About A.D. 1500 and extending to about A.D. 1850 or later, an A horizon formed on the sand sheet, probably in response to a desert grassland vegetation during the period of wet climate of the Little Ice Age. In an anthropogenic third phase of eolian activity, after A.D. 1850, the vegetation was likely disturbed by overgrazing; and the unit 2 and A horizon (unit 3) sands were deflated, resulting in the deposition of a thin layer of massive eolian sand (unit 4) across the sand sheet. By about A.D. 1900 mesquite shrubs had increased in abundance; and deflated sand, largely from unit 2, began to accumulate around the shrubs, forming coppice dunes (unit 5). Mesquite coppice dunes continued to increase in number and volume during the twentieth

The dynamic monitoring of aeolian desertification land distribution and its response to climate change in northern China

NASA Astrophysics Data System (ADS)

Feng, Lili; Jia, Zhiqing; Li, Qingxue

2016-12-01

Aeolian desertification is poorly understood despite its importance for indicating environment change. Here we exploit Gaofen-1(GF-1) and Moderate Resolution Imaging Spectroradiometer (MODIS) data to develop a quick and efficient method for large scale aeolian desertification dynamic monitoring in northern China. This method, which is based on Normalized Difference Desertification Index (NDDI) calculated by band1 & band2 of MODIS reflectance data (MODIS09A1). Then we analyze spatial-temporal change of aeolian desertification area and detect its possible influencing factors, such as precipitation, temperature, wind speed and population by Convergent Cross Mapping (CCM) model. It suggests that aeolian desertification area with population indicates feedback (bi-directional causality) between the two variables (P < 0.05), but forcing of aeolian desertification area by population is weak. Meanwhile, we find aeolian desertification area is significantly affected by temperature, as expected. However, there is no obvious forcing for the aeolian desertification area and precipitation. Aeolian desertification area with wind speed indicates feedback (bi-directional causality) between the two variables with significant signal (P < 0.01). We infer that aeolian desertification is greatly affected by natural factors compared with anthropogenic factors. For the desertification in China, we are greatly convinced that desertification prevention is better than control.

The dynamic monitoring of aeolian desertification land distribution and its response to climate change in northern China

PubMed Central

Feng, Lili; Jia, Zhiqing; Li, Qingxue

2016-01-01

Aeolian desertification is poorly understood despite its importance for indicating environment change. Here we exploit Gaofen-1(GF-1) and Moderate Resolution Imaging Spectroradiometer (MODIS) data to develop a quick and efficient method for large scale aeolian desertification dynamic monitoring in northern China. This method, which is based on Normalized Difference Desertification Index (NDDI) calculated by band1 & band2 of MODIS reflectance data (MODIS09A1). Then we analyze spatial-temporal change of aeolian desertification area and detect its possible influencing factors, such as precipitation, temperature, wind speed and population by Convergent Cross Mapping (CCM) model. It suggests that aeolian desertification area with population indicates feedback (bi-directional causality) between the two variables (P < 0.05), but forcing of aeolian desertification area by population is weak. Meanwhile, we find aeolian desertification area is significantly affected by temperature, as expected. However, there is no obvious forcing for the aeolian desertification area and precipitation. Aeolian desertification area with wind speed indicates feedback (bi-directional causality) between the two variables with significant signal (P < 0.01). We infer that aeolian desertification is greatly affected by natural factors compared with anthropogenic factors. For the desertification in China, we are greatly convinced that desertification prevention is better than control. PMID:28004798

Enriching acid rock drainage related microbial communities from surface-deposited oil sands tailings.

PubMed

Dean, Courtney; Xiao, Yeyuan; Roberts, Deborah J

2016-10-01

Little is known about the microbial communities native to surface-deposited pyritic oil sands tailings, an environment where acid rock drainage (ARD) could occur. The goal of this study was to enrich sulfur-oxidizing organisms from these tailings and determine whether different populations exist at pH levels 7, 4.5, and 2.5. Using growth-based methods provides model organisms for use in the future to predict potential activities and limitations of these organisms and to develop possible control methods. Thiosulfate-fed enrichment cultures were monitored for approximately 1 year. The results showed that the enrichments at pH 4.5 and 7 were established quicker than at pH 2.5. Different microbial community structures were found among the 3 pH environments. The sulfur-oxidizing microorganisms identified were most closely related to Halothiobacillus neapolitanus, Achromobacter spp., and Curtobacterium spp. While microorganisms related to Chitinophagaceae and Acidocella spp. were identified as the only possible iron-oxidizing and -reducing microbes. These results contribute to the general knowledge of the relatively understudied microbial communities that exist in pyritic oil sands tailings and indicate these communities may have a potential role in ARD generation, which may have implications for future tailings management.

Sedimentary structures and textures of Rio Orinoco channel sands, Venezuela and Colombia

USGS Publications Warehouse

McKee, Edwin Dinwiddie

1989-01-01

Most sedimentary structures represented in sand bodies of the Rio Orinoco are tabular-planar cross-strata which, together with some wedge-planar cross-strata, are the products of sand-wave deposition. Locally, in areas of river meander where point bars characteristically form, trough structures forming festoon patterns are numerous. At a few localities, sets of nearly horizontal strata occur between tabular-planar sets and are interpreted to be the deposits of very fast currents of the upper flow regime; elsewhere, uncommon lenses and beds of silt, clay, or organic matter consisting of leaves and twigs, seem to be the result of quiet-water settling through gravity. By far the most common grain size represented in the tabular-planar and wedge-planar cross-strata of the sandwave deposits is medium sand (? - ? millimeter) as determined by screen analyses. Many samples, however, also contain moderate quantities of coarse or very coarse sand. Eolian dunes on top of the sand-wave deposits are dominantly fine grained. The river channel sands were determined to be largely moderately well sorted, although in some places they were mostly well sorted, and in others, mostly moderately sorted.

Spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region (Alberta, Canada)

NASA Astrophysics Data System (ADS)

Cooke, Colin A.; Kirk, Jane L.; Muir, Derek C. G.; Wiklund, Johan A.; Wang, Xiaowa; Gleason, Amber; Evans, Marlene S.

2017-12-01

The mining and processing of the Athabasca oil sands (Alberta, Canada) has been occurring for decades; however, a lack of consistent regional monitoring has obscured the long-term environmental impact. Here, we present sediment core results to reconstruct spatial and temporal patterns in trace element deposition to lakes in the Athabasca oil sands region. Early mining operations (during the 1970s and 1980s) led to elevated V and Pb inputs to lakes located <50 km from mining operations. Subsequent improvements to mining and upgrading technologies since the 1980s have reduced V and Pb loading to near background levels at many sites. In contrast, Hg deposition increased by a factor of ~3 to all 20 lakes over the 20th century, reflecting global-scale patterns in atmospheric Hg emissions. Base cation deposition (from fugitive dust emissions) has not measurably impacted regional lake sediments. Instead, results from a principal components analysis suggest that the presence of carbonate bedrock underlying lakes located close to development appears to exert a first-order control over lake sediment base cation concentrations and overall lake sediment geochemical composition. Trace element concentrations generally did not exceed Canadian sediment quality guidelines, and no spatial or temporal trends were observed in the frequency of guideline exceedence. Our results demonstrate that early mining efforts had an even greater impact on trace element cycling than has been appreciated previously, placing recent monitoring efforts in a critical long-term context.

Elevated Nitrogen Deposition from Alberta Oil Sands Development Stimulates Phosphatase Activity in Dominant Sphagnum Moss Species

NASA Astrophysics Data System (ADS)

Kashi, N. N.; Wieder, R.; Vile, M. A.

2013-12-01

Emissions of NOx associated with Alberta oil sands (AOS) development are leading to locally elevated atmospheric N deposition, in a region where background N deposition has been historically quite low (< 1 kg/ha/yr). This elevated N deposition has the potential to alter the ecosystem structure and function of nutrient-poor boreal peatlands. Nitrogen enrichment may alter soil microbial activity, which could be manifested in changes in extracellular enzyme activities. Since 2011, we have been experimentally adding N as NH4NO3 in simulated precipitation at 0, 5, 10, 15, 20, and 25 kg N ha/yr/ plus no-water controls to a boreal bog and a poor fen (3 replicate plots per treatment). In 2013, acid phosphatase activities in living plant capitulum of Sphagnum angustifolium, Sphagnum fuscum, and Sphagnum magellanicum were quantified in June and July using 4-methyumbelliferylphosphate and fluorescence detection of the enzymatically released methylumbelliferone (MUF). Phosphatase activities did not differ with N treatment for S. angustifolium in the bog (p=0.3409) or the poor fen (p=0.0629), or for S. fuscum in the bog (p=0.1950), averaging 35.0 × 0.7, 61.6 × 1.2, and 41.6 × 0.9 μmol MUF/g DWT/hr, respectively. For S. fuscum in the poor fen, phosphatase activities differed between N treatments (p=0.0275), ranging 40.6 × 1.1 μmol MUF/g DWT/hr in the control plots to 73.7 × 2.0 μmol MUF/g DWT/hr in the 5 kg/ha/yr N treatment plots; increasing N deposition did not result in a gradual change in enzyme activity. On the other hand, S. magellanicum phosphatase activities differed between N treatments (p=0.0189) and showed a pattern of generally increasing activity with increasing N deposition (37.4 × 0.5 μmol MUF/g DWT/hr in control plots; 97.9 × 4.5 μmol MUF/g DWT/hr in the 25 kg/ha/yr N treatment plots). The differing phosphatase responses between these dominant Sphagnum species suggest unique differences in nutrient balance and/or microbial activity. Combining the

Sand wave fields beneath the Loop Current, Gulf of Mexico: Reworking of fan sands

USGS Publications Warehouse

Kenyon, Neil H.; Akhmetzhanov, A.M.; Twichell, D.C.

2002-01-01

Extensive fields of large barchan-like sand waves and longitudinal sand ribbons have been mapped by deep-towed SeaMARC IA sidescan sonar on part of the middle and lower Mississippi Fan that lies in about 3200 m of water. The area is beneath the strongly flowing Loop Current. The bedforms have not been adequately sampled but probably consist of winnowed siliciclastic-foraminiferal sands. The size (about 200 m from wingtip to wingtip) and shape of the large barchans is consistent with a previously observed peak current speed of 30 cm/s, measured 25 m above the seabed. The types of small-scale bedforms and the scoured surfaces of chemical crusts, seen on nearby bottom photographs, indicate that near-bed currents in excess of 30 cm/s may sometimes occur. At the time of the survey the sand transport direction was to the northwest, in the opposite direction to the Loop Current but consistent with there being a deep boundary current along the foot of the Florida Escarpment. Some reworking of the underlying sandy turbidites and debris flow deposits is apparent on the sidescan sonar records. Reworking by deep-sea currents, resulting in erosion and in deposits characterised by coarsening upwards structures and cross-bedding, is a process that has been proposed for sand found in cores in shallower parts of the Gulf of Mexico. This process is more widespread than hitherto supposed. 

Controls on the abruptness of gravel-sand transitions

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Exceptional marine sand bodies in the Paleozoic of Oklahoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fritz, R.D.; Kuykendall, M.D.; Hooker, E.O.

Of the wide variety of sandstone reservoirs in Oklahoma, the most unusual types of sand bodies are present in the Atokan Spiro Sandstone, Devonian Misener Sandstone, and Morrowan lower Morrow Sandstone. The common factors are that upon correlation and mapping these units are channel-like (fluvial-deltaic) in geometry, but from petrographic evidence are quartz-rich shallow-marine units, with the exclusion of intraclastic and diagenetic constituents. Stratigraphic mapping of the Spiro Sandstone of the Arkoma basin indicates two types of sand bodies: channel and sheet. The marine channel-like deposits, 10-150 ft thick, probably were deposited on a paleosurface produced by a pre-Atokan unconformity.more » Examination of cores and outcrop indicate that both the channel and sheet Spiro sands contain shallow-marine fossils, limestones, peloidal chamosite, burrows, and bioturbation, all indicative of a shallow-marine setting. The Misener Sandstone of north-central Oklahoma ranges from 10 to 100 ft thick with sharp boundaries. It was deposited in pre-Frisco/Woodford eroded paleochannels. Core evidence for shallow-marine deposition is glauconite, phosphatic fossils and clasts, burrows, and bioturbation. These were probably deposited in an embayed, estuary-like environment. The lower Morrow Sandstone of the Anadarko basin is similar in geometry, except that the sand bodies are multistoried and multilateral and do not appear to be associated with a regional unconformity. The lower Morrow sandstones, usually 30-60 ft thick. commonly are elongated and deposited parallel to the shoreline. Deposition is inferred to be shallow-marine from marine fossils and glauconite.« less

Dune-Yardang Interactions in Becquerel Crater, Mars.

PubMed

Urso, Anna; Chojnacki, Matthew; Vaz, David A

2018-01-01

Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars' recent history has been dominated by wind-driven activity. Resultantly, Martian landscapes often exhibit large-scale aeolian features, including yardang landforms carved from sedimentary-layered deposits. High-resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune-yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16-40 μm yr -1 ) would yield a formation time of 1.8-4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size-frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian-driven landscape evolution on Mars.

Dune-Yardang Interactions in Becquerel Crater, Mars

NASA Astrophysics Data System (ADS)

Urso, Anna; Chojnacki, Matthew; Vaz, David A.

2018-02-01

Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars' recent history has been dominated by wind-driven activity. Resultantly, Martian landscapes often exhibit large-scale aeolian features, including yardang landforms carved from sedimentary-layered deposits. High-resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune-yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16-40 μm yr-1) would yield a formation time of 1.8-4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size-frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian-driven landscape evolution on Mars.

Geomorphology context and characterization of dunefields developed by the southern westerlies at drying Colhué Huapi shallow lake, Patagonia Argentina

NASA Astrophysics Data System (ADS)

Montes, Alejandro; Rodríguez, Silvana Soledad; Domínguez, Carlos Eduardo

2017-10-01

Patagonia is the only continental territory exposed to the southern westerlies. The speed and frequency of these westerly winds generate a landscape strongly influenced by aeolian processes. This research shows a characterization of depositional and erosive aeolian landforms developed in dunefields associated to Lake Colhué Huapi, in the Extra-Andean Patagonia. Dunefields are located at 45°-46°S and moved in west-east direction due to the southern westerlies. We identified two big groups of active dunefields, one migrating through the dry lakebed of Colhué Huapi and the other migrating eastwards from the lakeshore. The dunefields mainly consist of transverse dunes, barchans, sand shadows and sand sheets. Yardangs, desert pavements, exhumed roots and decapitated soils were recognized in interdune areas. Longitudinal sand ridges, parallel to the prevailing wind direction, often remain preserved after the dunefields have passed. This allows to recognize the path of the dunes in the past. Sand ridges are recognized up to 28 km east from the present coast of the lake and evidenced former dunefields development. We describe the geomorphology context, landforms and sediments supply of dunefields related to the lake dynamics subject to clear tendency to desiccation.

Mid-Cretaceous aeolian desert systems in the Yunlong area of the Lanping Basin, China: Implications for palaeoatmosphere dynamics and paleoclimatic change in East Asia

NASA Astrophysics Data System (ADS)

Li, Gaojie; Wu, Chihua; Rodríguez-López, Juan Pedro; Yi, Haisheng; Xia, Guoqing; Wagreich, Michael

2018-02-01

The mid-Cretaceous constitutes a period of worldwide atmospheric and oceanic change associated with slower thermohaline circulation and ocean anoxic events, possible polar glaciations and by a changing climate pattern becoming controlled by a zonal planetary wind system and an equatorial humid belt. During the mid-Cretaceous, the subtropical high-pressure arid climate belt of the planetary wind system controlled the palaeolatitude distribution of humid belts in Asia as well as the spatial distribution of rain belts over the massive continental blocks at mid-low latitudes in the southern and northern hemispheres. Additionally, the orographic effect of the Andean-type active continental margin in East Asia hindered the transportation of ocean moisture to inland regions. With rising temperatures and palaeoatmospheric conditions dominated by high pressure systems, desert climate environments expanded at the inland areas of East Asia including those accumulated in the mid-Cretaceous of the Simao Basin, the Sichuan Basin, and the Thailand's Khorat Basin, and leading the Late Cretaceous erg systems in the Xinjiang Basin and Jianghan Basin. This manuscript presents evidences that allow to reinterpret previously considered water-laid sediments to be accumulated as windblown deposits forming part of extensive erg (sandy desert) systems. Using a multidisciplinary approach including petrological, sedimentological and architectural observations, the mid-Cretaceous (Albian-Turonian) Nanxin Formation from the Yunlong region of Lanping Basin, formerly considered to aqueous deposits is here interpreted as representing aeolian deposits, showing local aeolian-fluvial interaction deposits. The palaeowind directions obtained from the analysis of aeolian dune cross-beddings indicates that inland deserts were compatible with a high-pressure cell (HPC) existing in the mid-low latitudes of East Asia during the mid-Cretaceous. Compared with the Early Cretaceous, the mid-Cretaceous had

Aeolian Landscape Change in West Greenland

NASA Astrophysics Data System (ADS)

Heindel, Ruth Chaves

In the Arctic, aeolian processes can be important drivers of landscape change. Soil deflation, the removal of fine-grained sediment by wind, is one aeolian process that has had a profound impact in the Arctic. While soil deflation has been well studied in Iceland, our understanding of aeolian processes across the rest of the Arctic remains limited. Kangerlussuaq, West Greenland, provides an opportunity to study the mechanisms and impacts of soil deflation without direct anthropogenic influence. In Kangerlussuaq, strong katabatic winds have resulted in distinct erosional landforms, here referred to as deflation patches, that are largely devoid of vascular plants and are dominated by biological soil crusts. This dissertation considers the geomorphic and ecological impacts of soil deflation through an interdisciplinary framework. I show that deflation patches are a critical component of the Kangerlussuaq ecosystem, accounting for 22% of the terrestrial landscape and impacting vegetation dynamics by providing habitat for graminoid, herbaceous, and lichen species. Deflation patches formed roughly 230-800 years ago, during a period of cold, dry, and windy climate conditions. Deflation patches expand across the landscape when the active margin, or scarp, becomes undercut and collapses. I estimate that rates of patch expansion are roughly 2.5 cm yr-1, and that geomorphic change can be detected even over the short time period of two years. I suggest that an erosional threshold exists because climate conditions required for initial deflation-patch formation are harsher than those required for continued patch expansion. The future trajectory of deflation patches depends on the role of the biological soil crust as either a successional facilitator or a long-term landscape cover, as well as future climate conditions. While the biological soil crusts slightly enrich soil fertility over time, they decrease soil moisture and create an impenetrable soil surface, which may inhibit

Ground robotic measurement of aeolian processes

USDA-ARS?s Scientific Manuscript database

Models of aeolian processes rely on accurate measurements of the rates of sediment transport by wind, and careful evaluation of the environmental controls of these processes. Existing field approaches typically require intensive, event-based experiments involving dense arrays of instruments. These d...

Behavior of Windblown Sand on Mars: Results from Single-Particle Experiments

NASA Technical Reports Server (NTRS)

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

1999-01-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG&G Program. Because the martian aeolian environment in both high energy and of long duration, the most mobile fractions of windblown sand should have eradicated themselves by attrition, unless sand supply has kept pace with destruction. It is therefore important to understand the rate of grain attrition in order to make sense of the existence of vast dune fields on Mars. Attrition, has been addressed in other studies, but precise data for a single saltating grain striking a loose bed of sand have not been acquired -- the quintessential case to be understood for dunes on Mars. To acquire these data, we are employing a compound crossbow which has the bolt-firing mechanism replaced with a pneumatically-automated sabot system. The sabot can launch individual grains of sand of any size between several millimeters and about 50 microns, at velocities up to 100m/s. This is around the maximum velocity expected for saltating grains on Mars. The sabot sled is equipped with photoelectric sensors for measuring shot velocity. Baffling of the grain's exit orifice has enabled projection of single grains without significant aerodynamic effects from the sabot. Grains are fired into loose beds of sand at about 15 degrees from the horizontal (typical saltation trajectory at impact) while being

Behavior of Windblown Sand on Mars: Results from Single-Particle Experiments

NASA Astrophysics Data System (ADS)

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

1999-09-01

Experiments are investigating the behavior of individual sand grains in the high-energy martian aeolian regime. Energy partitioning during impact of a saltating grain determines grain longevity, but it also influences the way in which the bed becomes mobilized by reptation. When single grains of sand are fired into loose beds, the bed can absorb up to 90% of the impact energy by momentum transfer to other grains; it has been discovered that the impacting grains cause circular craters even at low impact angles. Hundreds of grains can be splashed by a single high-velocity (100 m/s) impact causing more bed disturbance through reptation than previously thought. The research is supported by NASA's PG&G Program. Because the martian aeolian environment in both high energy and of long duration, the most mobile fractions of windblown sand should have eradicated themselves by attrition, unless sand supply has kept pace with destruction. It is therefore important to understand the rate of grain attrition in order to make sense of the existence of vast dune fields on Mars. Attrition, has been addressed in other studies, but precise data for a single saltating grain striking a loose bed of sand have not been acquired -- the quintessential case to be understood for dunes on Mars. To acquire these data, we are employing a compound crossbow which has the bolt-firing mechanism replaced with a pneumatically-automated sabot system. The sabot can launch individual grains of sand of any size between several millimeters and about 50 microns, at velocities up to 100m/s. This is around the maximum velocity expected for saltating grains on Mars. The sabot sled is equipped with photoelectric sensors for measuring shot velocity. Baffling of the grain's exit orifice has enabled projection of single grains without significant aerodynamic effects from the sabot. Grains are fired into loose beds of sand at about 15 degrees from the horizontal (typical saltation trajectory at impact) while being

Wind-driven particle mobility on Mars: Insights from Mars Exploration Rover observations at "El Dorado" and surroundings at Gusev Crater

USGS Publications Warehouse

Sullivan, R.; Arvidson, R.; Bell, J.F.; Gellert, Ralf; Golombek, M.; Greeley, R.; Herkenhoff, K.; Johnson, J.; Thompson, S.; Whelley, P.; Wray, J.

2008-01-01

The ripple field known as 'El Dorado' was a unique stop on Spirit's traverse where dust-raising, active mafic sand ripples and larger inactive coarse-grained ripples interact, illuminating several long-standing issues of Martian dust mobility, sand mobility, and the origin of transverse aeolian ridges. Strong regional wind events endured by Spirit caused perceptible migration of ripple crests in deposits SSE of El Dorado, erasure of tracks in sandy areas, and changes to dust mantling the site. Localized thermal vortices swept across El Dorado, leaving paths of reduced dust but without perceptibly damaging nearly cohesionless sandy ripple crests. From orbit, winds responsible for frequently raising clay-sized dust into the atmosphere do not seem to significantly affect dunes composed of (more easily entrained) sand-sized particles, a long-standing paradox. This disparity between dust mobilization and sand mobilization on Mars is due largely to two factors: (1) dust occurs on the surface as fragile, low-density, sand-sized aggregates that are easily entrained and disrupted, compared with clay-sized air fall particles; and (2) induration of regolith is pervasive. Light-toned bed forms investigated at Gusev are coarse-grained ripples, an interpretation we propose for many of the smallest linear, light-toned bed forms of uncertain origin seen in high-resolution orbital images across Mars. On Earth, wind can organize bimodal or poorly sorted loose sediment into coarse-grained ripples. Coarse-grained ripples could be relatively common on Mars because development of durable, well-sorted sediments analogous to terrestrial aeolian quartz sand deposits is restricted by the lack of free quartz and limited hydraulic sediment processing. Copyright 2008 by the American Geophysical Union.

Plant Community and Nitrogen Deposition as Drivers of Alpha and Beta Diversities of Prokaryotes in Reconstructed Oil Sand Soils and Natural Boreal Forest Soils.

PubMed

Masse, Jacynthe; Prescott, Cindy E; Renaut, Sébastien; Terrat, Yves; Grayston, Sue J

2017-05-01

The Athabasca oil sand deposit is one of the largest single oil deposits in the world. Following surface mining, companies are required to restore soil-like profiles that can support the previous land capabilities. The objective of this study was to assess whether the soil prokaryotic alpha diversity (α-diversity) and β-diversity in oil sand soils reconstructed 20 to 30 years previously and planted to one of three vegetation types (coniferous or deciduous trees and grassland) were similar to those found in natural boreal forest soils subject to wildfire disturbance. Prokaryotic α-diversity and β-diversity were assessed using massively parallel sequencing of 16S rRNA genes. The β-diversity, but not the α-diversity, differed between reconstructed and natural soils. Bacteria associated with an oligotrophic lifestyle were more abundant in natural forest soils, whereas bacteria associated with a copiotrophic lifestyle were more abundant in reconstructed soils. Ammonia-oxidizing archaea were most abundant in reconstructed soils planted with grasses. Plant species were the main factor influencing α-diversity in natural and in reconstructed soils. Nitrogen deposition, pH, and plant species were the main factors influencing the β-diversity of the prokaryotic communities in natural and reconstructed soils. The results highlight the importance of nitrogen deposition and aboveground-belowground relationships in shaping soil microbial communities in natural and reconstructed soils. IMPORTANCE Covering over 800 km 2 , land disturbed by the exploitation of the oil sands in Canada has to be restored. Here, we take advantage of the proximity between these reconstructed ecosystems and the boreal forest surrounding the oil sand mining area to study soil microbial community structure and processes in both natural and nonnatural environments. By identifying key characteristics shaping the structure of soil microbial communities, this study improved our understanding of how

A Global Digital Database and Atlas of Quaternary Dune Fields and Sand Seas

NASA Astrophysics Data System (ADS)

Lancaster, N.; Halfen, A. F.

2012-12-01

Sand seas and dune fields are globally significant sedimentary deposits, which archive the effects of climate and sea level change on a variety of temporal and spatial scales. Dune systems provide a valuable source of information on past climate conditions, including evidence for periods of aridity and unique data on past wind regimes. Researchers have compiled vast quantities of geomorphic and chronological data from these dune systems for nearly half a century, however, these data remain disconnected, making comparisons of dune systems challenging at global and regional scales. The primary goal of this project is to develop a global digital database of chronologic information for periods of desert sand dune accumulation and stabilization, as well as, pertinent stratigraphic and geomorphic information. This database can then be used by scientists to 1) document the history of aeolian processes in arid regions with emphasis on dune systems in low and mid latitude deserts, 2) correlate periods of sand accumulation and stability with other terrestrial and marine paleoclimatic proxies and records, and 3) develop an improved understanding of the response of dune systems to climate change. The database currently resides in Microsoft Access format, which allows searching and filtering of data. The database includes 4 linked tables containing information on the site, chronological control (radiocarbon or luminescence), and the pertinent literature citations. Thus far the database contains information for 838 sites world wide, comprising 2598 luminescence and radiocarbon ages, though these numbers increase regularly as new data is added. The database is only available on request at this time, however, an online, GIS database is being developed and will be available in the near future. Data outputs from the online database will include PDF reports and Google Earth formatted data sets for quick viewing of data. Additionally, data will be available in a gridded format for

Aeolian and fluvial processes in dryland regions: the need for integrated studies

USGS Publications Warehouse

Belnap, Jayne; Munson, Seth M.; Field, Jason P.

2011-01-01

Aeolian and fluvial processes play a fundamental role in dryland regions of the world and have important environmental and ecological consequences from local to global scales. Although both processes operate over similar spatial and temporal scales and are likely strongly coupled in many dryland systems, aeolian and fluvial processes have traditionally been studied separately, making it difficult to assess their relative importance in drylands, as well as their potential for synergistic interaction. Land degradation by accelerated wind and water erosion is a major problem throughout the world's drylands, and although recent studies suggest that these processes likely interact across broad spatial and temporal scales to amplify the transport of soil resources from and within drylands, many researchers and land managers continue to view them as separate and unrelated processes. Here, we illustrate how aeolian and fluvial sediment transport is coupled at multiple spatial and temporal scales and highlight the need for these interrelated processes to be studied from a more integrated perspective that crosses traditional disciplinary boundaries. Special attention is given to how the growing threat of climate change and land-use disturbance will influence linkages between aeolian and fluvial processes in the future. We also present emerging directions for interdisciplinary needs within the aeolian and fluvial research communities that call for better integration across a broad range of traditional disciplines such as ecology, biogeochemistry, agronomy, and soil conservation.

Early Islamic inter-settlement agroecosystems in coastal sand, Yavneh dunefield, eastern Mediterranean coast, Israel

NASA Astrophysics Data System (ADS)

Roskin, Joel; Taxel, Itamar

2017-04-01

This study reveals an attempt to condition agriculture in coastal aeolian sand holding a high water table. Twenty-six small sites, clustering in topographic lows of the Yavneh dunefield, southern Israeli coastal plain, yield surficial Early Islamic finds, and eroded 1-2 m high berms built of grey sand partially covered by parabolic and transverse dunes. Small winter ponds develop by some of the sites. A clay loam 2.5 m beneath the surface retains the water table at a depth of 2.2 m. Between the berms, a 10-50 cm thick grey sand unit dating by OSL to 0.9 ka (11th-12th century AD) underlays a loose aeolian sand cover and overlays sand whose upper parts date to 1.1 ka (9th-10th century AD). The grey unit displays slightly improved fertility (phosphate, potassium, nitrogen and calcium carbonate) in relation to the underlying sand suggesting an anthropogenic enrichment of ash and refuse. Particle size is similar to the sand. Organic carbon and magnetic susceptibility values (0-5 SI) values are quite low (0.4-0.8%) for both units. The artifact assemblage is mixed and comprised of small (<10 cm) pottery sherds, ceramic roof tiles, glass, marble and granite fragments, mosaic tesserae, pottery production waste, iron slag, animal bones, seashells, and coins dated between the 8th and 10th century. The artifacts pre-date the OSL age of the underlying grey sand. The pottery shares many characteristics with the rich ceramic assemblage of nearby inland Yavneh. The establishment of the sites may have been executed by the inhabitants of either Yavneh (or another major inland settlement) or the seashore Muslim military stronghold of Yavneh-Yam (Taxel, 2013). The density of the sites is remarkable compared with the paucity of Byzantine sites in the same region, indicating a distinct spatial pattern that served a specific purpose. The lack of buried artifacts and structures suggests that the sites did not serve for permanent/intensive occupation. The widespread utilization of the rich

Modelling spiky acceleration response of dilative sand deposits during earthquakes with emphasis on large post-liquefaction deformation

NASA Astrophysics Data System (ADS)

Wang, Gang; Wei, Xing; Zhao, John

2018-01-01

The acceleration records at some liquefied sand deposits exhibit a distinctive spiky waveform, characterized by strong amplification and high-frequency components. A comprehensive constitutive model was used to analyze the mechanism of such spiky acceleration responses. An idealized single-degree-of-freedom (SDF) system was constructed, in which the force-displacement relation of the spring follows the stress-strain behavior of saturated sand during undrained shearing. The SDF system demonstrated that the spikes are directly related to the strain-hardening behavior of sand during post-liquefaction cyclic shearing. Furthermore, there exists a threshold shear strain length, which is in accordance with the limited amplitude of the fluid-like shear strain generated at instantaneous zero effective stress state during the post-liquefaction stage. The spiky acceleration can only occur when the cyclic shear strain exceeds the threshold shear strain length. It is also revealed that the time intervals between the acceleration spikes increase gradually along with the continuation of shaking because the threshold shear strain length increases gradually and then more time is needed to generate larger shear strain to cause strain hardening. Records at the Kushiro Port site and Port Island site during past earthquakes are simulated through the fully coupled method to validate the presented mechanism.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oblad, A.G.; Dahlstrom, D.A.; Deo, M.D.

1997-11-26

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

Connecting meteorology to surface transport in aeolian landscapes: Peering into the boundary layer with Doppler lidar

NASA Astrophysics Data System (ADS)

Gunn, A.; Jerolmack, D. J.; Edmonds, D. A.; Ewing, R. C.; Wanker, M.; David, S. R.

2017-12-01

Aolian sand dunes grow to 100s or 1000s of meters in wavelength by sand saltation, which also produces dust plumes that feed cloud formation and may spread around the world. The relations among sediment transport, landscape dynamics and wind are typically observed at the limiting ends of the relevant range: highly resolved and localized ground observations of turbulence and relevant fluxes; or regional and synoptic-scale meteorology and satellite imagery. Between the geostrophic winds aloft and shearing stress on the Earth's surface is the boundary layer, whose stability and structure determines how momentum is transferred and ultimately entrains sediment. Although the literature on atmospheric boundary layer flows is mature, this understanding is rarely applied to aeolian landscape dynamics. Moreover, there are few vertically and time-resolved datasets of atmospheric boundary layer flows in desert sand seas, where buoyancy effects are most pronounced. Here we employ a ground-based upward-looking doppler lidar to examine atmospheric boundary layer flow at the upwind margin of the White Sands (New Mexico) dune field, providing continuous 3D wind velocity data from the surface to 300-m aloft over 70 days of the characteristically windy spring season. Data show highly resolved daily cyles of convective instabilty due to daytime heating and stable stratification due to nightime cooling which act to enhance or depress, respectively, the surface wind stresses for a given free-stream velocity. Our data implicate convective instability in driving strong saltation and dust emission, because enhanced mixing flattens the vertical velocity profile (raising surface wind speed) while upward advection helps to deliver dust to the high atmosphere. We also find evidence for Ekman spiralling, with a magnitude that depends on atmospheric stability. This spiralling gives rise to a deflection in the direction between geostrophic and surface winds, that is significant for the

Long-term dynamic characterization of aeolian desertification in northwest Shanxi, China.

PubMed

Xue, Zhanjin; Qin, Zuodong; Cheng, Fangqin; Ding, Guangwei; Li, Hongjian

2017-07-01

Northwest Shanxi is located on the farming-pastoral ecotone of northern China, where aeolian desertification is one of the most serious environmental and socioeconomic issues. The remote sensing image and geostatistical approach were implemented to estimate aeolian desertified land (ADL) dynamic variations from 1975 to 2015. Results showed that the ADL covered 11,685.21 km 2 (82.29%) of the study area in 2015, the majority of which was classified as a light or moderate degree. The area of ADL gradually expanded at an increasing rate of 87.37 km 2 a -1 during the 1975-2000 periods. More specifically, the area of ADL has increased by 1259.23 km 2 from 1975 to 1990 and by 924.96 km 2 from 1990 to 2000, respectively. In contrast, spatial transfer of ADL areas has dwindled by 2365.85 km 2 with a net decrease of 157.72 km 2 a -1 , and the mitigated areas of aeolian desertification were 10,602.24 km 2 between 2000 and 2015. During the past 40 years, the gravity center of ADL migrated to southeast until 2000 and moved northwest in 2000-2015. From 1975 to 2000, the migration distance of severe ADL was the largest, migrated toward the northwest by 19.03 km in 1975-1990 and by 20.16 km in 1990-2000, respectively. From 2000 to 2015, the migration distance of light ADL was the largest, 27.54 km migrated to the northwest. Aeolian desertification rapidly expanded from 1975 to 2000 under the combination of climate change and intensive human activities. Since the year of 2000, ecological engineering strategy initiated by the governments has been the dominant contributor to the aeolian desertification severity reversal. Aeolian desertification prevention is a complicated process. Both the central and local government should play a critical role in the rehabilitation of ADL in the long term.

NASA's Planetary Aeolian Laboratory: Status and Update

NASA Astrophysics Data System (ADS)

Williams, D. A.; Smith, J. K.

2017-05-01

This presentation provides a status update on the operational capabilities and funding plans by NASA for the Planetary Aeolian Laboratory located at NASA Ames Research Center, including details for those proposing future wind tunnel experiments.

Sediment connectivity at source-bordering aeolian dunefields along the Colorado River in the Grand Canyon, USA

NASA Astrophysics Data System (ADS)

Sankey, Joel; Kasprak, Alan; Caster, Joshua; East, Amy; Fairley, Helen

2017-04-01

Aeolian dunefields that are primarily built and maintained with river-derived sediment are found in many river valleys throughout the world and are impacted by changes in climate, land use, and river regulation. Quantifying the dynamic response of these aeolian dunefields to alterations in river flow is especially difficult given the highly correlated nature of the interacting geomorphic and sediment transport processes that drive their formation and maintenance. We characterize the effects of controlled river floods on changes in sediment connectivity at source-bordering aeolian dunefields in the Grand Canyon, USA. Controlled floods from the Glen Canyon Dam are used to build sandbars along the Colorado River in Grand Canyon which provide the main sediment source for aeolian dunefields. Aeolian dunefields are a primary resource of concern for land managers in the Grand Canyon because they often contain buried archaeological features. To characterize dunefield response to controlled floods, we use a novel, automated approach for the mechanistic segregation of geomorphic change to discern the geomorphic processes responsible for driving topographic change in very high resolution digital elevation models-of-difference (DODs) that span multiple, consecutive controlled river floods at source-bordering dunefields. We subsequently compare the results of mechanistic segregation with modelled estimates of aeolian dunefield evolution in order to understand how dunefields respond to contemporary, anthropogenically-driven variability in sediment supply and connectivity. These methods provide a rapid technique for sediment budgeting and enable the inference of spatial and temporal patterns in sediment flux between the fluvial and aeolian domains. We anticipate that this approach will be adaptable to other river valleys where the interactions of aeolian, fluvial, and hillslope processes drive sediment connectivity for the maintenance of source-bordering aeolian dunefields.

Surface properties of Mars' polar layered deposits and polar landing sites

USGS Publications Warehouse

Vasavada, Ashwin R.; Williams, Jean-Pierre; Paige, David A.; Herkenhoff, Ken E.; Bridges, Nathan T.; Greeley, Ronald; Murray, Bruce C.; Bass, Deborah S.; McBride, Karen S.

2000-01-01

On December 3, 1999, the Mars Polar Lander and Mars Microprobes will land on the planet's south polar layered deposits near (76°S, 195°W) and conduct the first in situ studies of the planet's polar regions. The scientific goals of these missions address several poorly understood and globally significant issues, such as polar meteorology, the composition and volatile content of the layered deposits, the erosional state and mass balance of their surface, their possible relationship to climate cycles, and the nature of bright and dark aeolian material. Derived thermal inertias of the southern layered deposits are very low (50-100 J m-2 s-1/2 K-1), suggesting that the surface down to a depth of a few centimeters is generally fine grained or porous and free of an appreciable amount of rock or ice. The landing site region is smoother than typical cratered terrain on ∼1 km pixel-1 Viking Orbiter images but contains low-relief texture on ∼5 to 100 m pixel-1 Mariner 9 and Mars Global Surveyor images. The surface of the southern deposits is older than that of the northern deposits and appears to be modified by aeolian erosion or ablation of ground ice.

Dune-Yardang Interactions in Becquerel Crater, Mars

PubMed Central

Urso, Anna; Chojnacki, Matthew; Vaz, David A.

2018-01-01

Isolated landscapes largely shaped by aeolian processes can occur on Earth, while the majority of Mars’ recent history has been dominated by wind-driven activity. Resultantly, Martian landscapes often exhibit large-scale aeolian features, including yardang landforms carved from sedimentary-layered deposits. High-resolution orbital monitoring has revealed that persistent bedform activity is occurring with dune and ripple migration implying ongoing abrasion of the surface. However, little is known about the interaction between dunes and the topography surrounding them. Here we explore dune-yardang interactions in Becquerel crater in an effort to better understand local landscape evolution. Dunes there occur on the north and south sides of a 700 m tall sedimentary deposit, which displays numerous superposed yardangs. Dune and yardang orientations are congruent, suggesting that they both were formed under a predominantly northerly wind regime. Migration rates and sediment fluxes decrease as dunes approach the deposit and begin to increase again downwind of the deposit where the effect of topographic sheltering decreases. Estimated sand abrasion rates (16–40 μm yr−1) would yield a formation time of 1.8–4.5 Myr for the 70 m deep yardangs. This evidence for local aeolian abrasion also helps explain the young exposure ages of deposit surfaces, as estimated by the crater size-frequency distribution. Comparisons to terrestrial dune activity and yardang development begin to place constraints on yardang formation times for both Earth and Mars. These results provide insight into the complexities of sediment transport on uneven terrain and are compelling examples of contemporary aeolian-driven landscape evolution on Mars. PMID:29564199

Application of Database Approaches to the Study of Earth's Aeolian Environments: Community Needs and Goals

NASA Astrophysics Data System (ADS)

Scuderi, Louis A.; Weissmann, Gary S.; Hartley, Adrian J.; Yang, Xiaoping; Lancaster, Nicholas

2017-08-01

Aeolian science is faced with significant challenges that impact its ability to benefit from recent advances in information technology. The discipline deals with high-end systems in the form of ground and satellite based sensors, computer modeling and simulation, and wind tunnel experiments. Aeolian scientists also collect field data manually with observational methods that may differ significantly between studies with little agreement on even basic morphometric parameters and terminology. Data produced from these studies, while forming the core of research papers and reports, is rarely available to the community at large. Recent advances are also superimposed on an underlying semantic structure that dates to the 1800's or earlier that is confusing, with ambiguously defined, and at times even contradictory, meanings. The aeolian "world-view" does not always fit within neat increments nor is defined by crisp objects. Instead change is continuous and features are fuzzy. Development of an ontological framework to guide spatiotemporal research is the fundamental starting point for organizing data in aeolian science. This requires a "rethinking" of how we define, collect, process, store and share data along with the development of a community-wide collaborative approach designed to bring the discipline into a data rich future. There is also a pressing need to develop efficient methods to integrate, analyze and manage spatial and temporal data and to promote data produced by aeolian scientists so it is available for preparing diagnostic studies, as input into a range of environmental models, and for advising national and international bodies that drive research agendas. This requires the establishment of working groups within the discipline to deal with content, format, processing pipelines, knowledge discovery tools and database access issues unique to aeolian science. Achieving this goal requires the development of comprehensive and highly-organized databases, tools

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edgar, Lauren A.; Gupta, Sanjeev; Rubin, David M.

This article characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification tomore » determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.« less

Shaler: in situ analysis of a fluvial sedimentary deposit on Mars

DOE PAGES

Edgar, Lauren A.; Gupta, Sanjeev; Rubin, David M.; ...

2017-03-09

This article characterizes the detailed sedimentology of a fluvial sandbody on Mars for the first time and interprets its depositional processes and palaeoenvironmental setting. Despite numerous orbital observations of fluvial landforms on the surface of Mars, ground-based characterization of the sedimentology of such fluvial deposits has not previously been possible. Results from the NASA Mars Science Laboratory Curiosity rover provide an opportunity to reconstruct at fine scale the sedimentary architecture and palaeomorphology of a fluvial environment on Mars. This work describes the grain size, texture and sedimentary facies of the Shaler outcrop, reconstructs the bedding architecture, and analyses cross-stratification tomore » determine palaeocurrents. On the basis of bedset geometry and inclination, grain-size distribution and bedform migration direction, this study concludes that the Shaler outcrop probably records the accretion of a fluvial barform. The majority of the outcrop consists of large-scale trough cross-bedding of coarse sand and granules. Palaeocurrent analyses and bedform reconstruction indicate that the beds were deposited by bedforms that migrated towards the north-east, across the surface of a bar that migrated south-east. Stacked cosets of dune cross-bedding suggest aggradation of multiple bedforms, which provides evidence for short periods of sustained flow during Shaler deposition. However, local evidence for aeolian reworking and the presence of potential desiccation cracks within the outcrop suggest that fluvial deposition may have been intermittent. The uppermost strata at Shaler are distinct in terms of texture and chemistry and are inferred to record deposition from a different sediment dispersal system with a contrasting provenance. The outcrop as a whole is a testament to the availability of liquid water on the surface of Mars in its early history.« less

Microdunes and other aeolian bedforms on Venus - Wind Tunnel simulations

NASA Technical Reports Server (NTRS)

Greeley, R.; Marshall, J. R.; Leach, R. N.

1984-01-01

The development of aeolian bedforms in the simulated Venusian environment has been experimentally studied in the Venus Wind Tunnel. It is found that the development of specific bedforms, including ripples, dunes, and 'waves', as well as their geometry, are controlled by a combination of factors including particle size, wind speed, and atmospheric density. Microdunes are formed which are analogous to full-size terrestrial dunes and are characterized by the development of slip faces, internal cross-bedding, a low ratio of saltation path length to dune length, and a lack of particle-size sorting. They begin to develop at wind speeds just above saltation threshold and evolve into waves at higher velocities. At wind speeds of about 1.5 m/sec and higher, the bed is flat and featureless. This evolution is explained by a model based on the interaction of alternating zones of erosion and deposition and particle saltation distances.

Microdunes and Other Aeolian Bedforms on Venus: Wind Tunnel Simulations

NASA Technical Reports Server (NTRS)

Greeley, R.; Marshall, J. R.; Leach, R. N.

1985-01-01

The development of aeolian bedforms in the simulated Venusian environment has been experimentally studied in the Venus Wind tunnel. It is found that the development of specific bedforms, including ripples, dunes, and waves, as well as their geometry, are controlled by a combination of factors including particle size, wind speed, and atmospheric density. Microdunes are formed which are analogous to full-size terrestrial dunes and are characterized by the development of slip faces, internal cross-bedding, a low ratio of saltation path length to dune length, and a lack of particle-size sorting. They begin to develop at wind speeds just above saltation threshold and evolve into waves at higher velocities. At wind speeds of about 1.5 m/sec and higher, the bed is flat and featureless. This evolution is explained by a model based on the interaction of alternating zones of erosion and deposition and particle saltation distances.

Geologic assessments and characterization of marine sand resources - Gulf of Mexico region

USGS Publications Warehouse

Williams, S. Jeffress; Cichon, Helana A.

1993-01-01

The U.S. Geological Survey conducts geologic surveys and research in marine areas of the United States and its territories and possessions. An objective in some of the investigations is locating and evaluating marine sand and gravel resources and interpretation of the origins of the sand body deposits. Results from such studies over the past 30 years show that many extremely large deposits are located close to expanding metropolitan areas, which have a need for aggregate materials for construction, and near-developed coastal areas, where beach replenishment may be used to mitigate coastal erosion. The Gulf of Mexico continental shelf from the Florida Peninsula to the Mexico border is an enormous area, but little attention has been directed on sand and gravel resources. Based on limited surveys, the total sand and gravel resources for the entire Gulf of Mexico is estimated to be 269 billion cubic meters. However, the sand tends to be fine-grained and is often mixed with mud; gravel deposits, except for shell, are mostly nonexistent.

Determination of erosion thresholds and aeolian dune stabilization mechanisms via robotic shear strength measurements

NASA Astrophysics Data System (ADS)

Qian, F.; Lee, D. B.; Bodek, S.; Roberts, S.; Topping, T. T.; Robele, Y.; Koditschek, D. E.; Jerolmack, D. J.

2017-12-01

Understanding the parameters that control the spatial variation in aeolian soil erodibility is crucial to the development of sediment transport models. Currently, in-situ measurements of erodibility are time consuming and lack robustness. In an attempt to remedy this issue, we perform field and laboratory tests to determine the suitability of a novel mechanical shear strength method to assess soil erodibility. These tests can be performed quickly ( 1 minute) by a semi-autonomous robot using its direct-drive leg, while environmental controls such as soil moisture and grain size are simultaneously characterized. The robot was deployed at White Sands National Monument to delineate and understand erodibility gradients at two different scales: (1) from dry dune crest to moist interdune (distance 10s m), where we determined that shear strength increases by a factor of three with increasing soil moisture; and (2) from barren barchan dunes to vegetated and crusted parabolics downwind (distance 5 km), where we found that shear strength was enhanced by a factor of two relative to loose sand. Interestingly, shear strength varied little from carbonate-crusted dune surfaces to bio-crust covered interdunes in the downwind parabolic region, indicating that varied surface crusts contribute similarly to erosion resistance. To isolate the control of soil moisture on erodibility, we performed laboratory experiments in a sandbox. These results verify that the observed increase in soil erodibility from barchan crest to interdune at White Sands is dominated by soil moisture, and the variation in parabolic dune and barchan interdune areas results from a combination of soil moisture, bio-activity, and crust development. This study highlights that spatial variation of soil erodibility in arid environments is large enough to significantly affect sediment transport, and that probing soil erodibility with a robot has the potential to improve our understanding of this multifaceted problem.

An enhanced approach for the use of satellite-derived leaf area index values in dry deposition modeling in the Athabasca oil sands region.

PubMed

Davies, Mervyn; Cho, Sunny; Spink, David; Pauls, Ron; Desilets, Michael; Shen, Yan; Bajwa, Kanwardeep; Person, Reid

2016-12-15

In the Athabasca oil sands region (AOSR) of Northern Alberta, the dry deposition of sulphur and nitrogen compounds represents a major fraction of total (wet plus dry) deposition due to oil sands emissions. The leaf area index (LAI) is a critical parameter that affects the dry deposition of these gaseous and particulate compounds to the surrounding boreal forest canopy. For this study, LAI values based on Moderate Resolution Imaging Spectroradiometer satellite imagery were obtained and compared to ground-based measurements, and two limitations with the satellite data were identified. The satellite LAI data firstly represents one-sided LAI values that do not account for the enhanced LAI associated with needle leaf geometry, and secondly, underestimates LAI in winter-time northern latitude regions. An approach for adjusting satellite LAI values for different boreal forest cover types, as a function of time of year, was developed to produce more representative LAI values that can be used by air quality sulphur and nitrogen deposition models. The application of the approach increases the AOSR average LAI for January from 0.19 to 1.40, which represents an increase of 637%. Based on the application of the CALMET/CALPUFF model system, this increases the predicted regional average dry deposition of sulphur and nitrogen compounds for January by factors of 1.40 to 1.30, respectively. The corresponding AOSR average LAI for July increased from 2.8 to 4.0, which represents an increase of 43%. This increases the predicted regional average dry deposition of sulphur and nitrogen compounds for July by factors of 1.28 to 1.22, respectively. These findings reinforce the importance of the LAI metric for predicting the dry deposition of sulphur and nitrogen compounds. While satellite data can provide enhanced spatial and temporal resolution, adjustments are identified to overcome associated limitations. This work is considered to have application for other deposition model studies where

Geologic map of Great Sand Dunes National Park, Colorado

USGS Publications Warehouse

Madole, Richard F.; VanSistine, D. Paco; Romig, Joseph H.

2016-10-20

Geologic mapping was begun after a range fire swept the area of what is now the Great Sand Dunes National Park in April 2000. The park spans an area of 437 square kilometers (or about 169 square miles), of which 98 percent is blanketed by sediment of Quaternary age, the Holocene and Pleistocene Epochs; hence, this geologic map of the Great Sand Dunes National Park is essentially a surficial geologic map. These surficial deposits are diverse and include sediment of eolian (windblown), alluvial (stream and sheetwash), palustrine (wetlands and marshes), lacustrine (lake), and mass-wasting (landslides) origin. Sediment of middle and late Holocene age, from about 8,000 years ago to the present, covers about 80 percent of the park.Fluctuations in groundwater level during Holocene time caused wetlands on the nearby lowland that bounds the park on the west to alternately expand and contract. These fluctuations controlled the stability or instability of eolian sand deposits on the downwind (eastern) side of the lowland. When groundwater level rose, playas became lakes, and wet or marshy areas formed in many places. When the water table rose, spring-fed streams filled their channels and valley floors with sediment. Conversely, when groundwater level fell, spring-fed streams incised their valley floors, and lakes, ponds, and marshes dried up and became sources of windblown sand.Discharge in streams draining the west flank of the Sangre de Cristo Range is controlled primarily by snowmelt and flow is perennial until it reaches the mountain front, beyond which streams begin losing water at a high rate as the water soaks into the creek beds. Even streams originating in the larger drainage basins, such as Sand and Medano Creeks, generally do not extend much more than 4 km (about 2.5 miles) beyond where they exit the mountains.The Great Sand Dunes contain the tallest dunes (maximum height about 750 feet, or 230 m) in North America. These dunes cover an area of 72 square kilometers

Mechanics of aeolian processes: Soil erosion and dust production

NASA Technical Reports Server (NTRS)

Mehrabadi, M. M.

1989-01-01

Aeolian (wind) processes occur as a result of atmosphere/land-surface system interactions. A thorough understanding of these processes and their physical/mechanical characterization on a global scale is essential to monitoring global change and, hence, is imperative to the fundamental goal of the Earth observing system (Eos) program. Soil erosion and dust production by wind are of consequence mainly in arid and semi arid regions which cover 36 percent of the Earth's land surface. Some recent models of dust production due to wind erosion of agricultural soils and the mechanics of wind erosion in deserts are reviewed and the difficulties of modeling the aeolian transport are discussed.

Ecohydrological implications of aeolian sediment trapping by sparse vegetation in drylands

USGS Publications Warehouse

Gonzales, Howell B.; Ravi, Sujith; Li, Junran; Sankey, Joel B.

2018-01-01

Aeolian processes are important drivers of ecosystem dynamics in drylands, and important feedbacks exist among aeolian – hydrological processes and vegetation. The trapping of wind-borne sediments by vegetation may result in changes in soil properties beneath the vegetation, which, in turn, can alter hydrological and biogeochemical processes. Despite the relevance of aeolian transport to ecosystem dynamics, the interactions between aeolian transport and vegetation in shaping dryland landscapes where sediment distribution is altered by relatively rapid changes in vegetation composition such as shrub encroachment, is not well understood. Here, we used a computational fluid dynamics (CFD) modeling framework to investigate the sediment trapping efficiencies of vegetation canopies commonly found in a shrub-grass ecotone in the Chihuahuan Desert (New Mexico, USA) and related the results to spatial heterogeneity in soil texture and infiltration measured in the field. A CFD open-source software package was used to simulate aeolian sediment movement through three-dimensional architectural depictions of Creosote shrub (Larrea tridentata) and Black Grama grass (Bouteloua eriopoda) vegetation types. The vegetation structures were created using a computer-aided design software (Blender), with inherent canopy porosities, which were derived using LIDAR (Light Detection and Ranging) measurements of plant canopies. Results show that considerable heterogeneity in infiltration and soil grain size distribution exist between the microsites, with higher infiltration and coarser soil texture under shrubs. Numerical simulations also indicate that the differential trapping of canopies might contribute to the observed heterogeneity in soil texture. In the early stages of encroachment, the shrub canopies, by trapping coarser particles more efficiently, might maintain higher infiltration rates leading to faster development of the microsites (among other factors) with enhanced ecological

Our evolving understanding of aeolian bedforms, based on observation of dunes on different worlds

NASA Astrophysics Data System (ADS)

Diniega, Serina; Kreslavsky, Mikhail; Radebaugh, Jani; Silvestro, Simone; Telfer, Matt; Tirsch, Daniela

2017-06-01

Dunes, dune fields, and ripples are unique and useful records of the interaction between wind and granular materials - finding such features on a planetary surface immediately suggests certain information about climate and surface conditions (at least during the dunes' formation and evolution). Additionally, studies of dune characteristics under non-Earth conditions allow for ;tests; of aeolian process models based primarily on observations of terrestrial features and dynamics, and refinement of the models to include consideration of a wider range of environmental and planetary conditions. To-date, the planetary aeolian community has found and studied dune fields on Mars, Venus, and the Saturnian moon Titan. Additionally, we have observed candidate ;aeolian bedforms; on Comet 67P/Churyumov-Gerasimenko, the Jovian moon Io, and - most recently - Pluto. In this paper, we hypothesize that the progression of investigations of aeolian bedforms and processes on a particular planetary body follows a consistent sequence - primarily set by the acquisition of data of particular types and resolutions, and by the maturation of knowledge about that planetary body. We define that sequence of generated knowledge and new questions (within seven investigation phases) and discuss examples from all of the studied bodies. The aim of such a sequence is to better define our past and current state of understanding about the aeolian bedforms of a particular body, to highlight the related assumptions that require re-analysis with data acquired during later investigations, and to use lessons learned from planetary and terrestrial aeolian studies to predict what types of investigations could be most fruitful in the future.

Studies in Martian Aeolian Geology

NASA Technical Reports Server (NTRS)

Greeley, Ronald

2001-01-01

This report gives the results from the investigation through March 15, 1999 for the first two years of the three year investigation (year 3 runs from March 1, 1999 to February 27, 2000). The investigation included three tasks, all involving windblown dust (particles a few micrometers in diameter) to simulate the aeolian regime on Mars. Experiments were conducted primarily in the Mars Surface Wind Tunnel (MARSWIT) at NASA-Ames Research Center.

An integrated OSL chronology, sedimentology and geochemical approach to loess deposits from Tuoji Island, Shandong Province: Implications for the late quaternary paleoenvironment in East China

NASA Astrophysics Data System (ADS)

Xu, Shujian; Kong, Fanbiao; Jia, Guangju; Miao, Xiaodong; Ding, Xinchao

2018-04-01

The Tuoji II (TJII) section on the Miaodao Islands in the Bohai Sea is a representative aeolian section off China's east coast. This study applied optically stimulated luminescence (OSL) dating, conducted grain size analysis, and examined major and trace element compositions, to investigate the loess-paleosol sequences. The OSL ages at depths of 0.6, 1.8, 2.8, 3.8, and 4.8 m were determined as 14.4 ± 0.4, 16.7 ± 1.3, 20.8 ± 1.0, 40.9 ± 1.5, and 47.9 ± 3.7 ka, respectively. It was projected that the loess started to accumulate at ca. 62.6 ka, according to presumed depositional rates. In this study, typical aeolian deposits elsewhere including the Luochuan (LC), Xiashu (XS), Wushan (WS), and Xifeng (XF) sections were compared with TJII section here. The results showed similarity in the geochemical characteristics of the deposits from the different areas of China and normalized upper continental crust, indicating aeolian origin of this island loess. In comparison with the LC, XS, WS, and XF samples, the aeolian deposits of the TJII section have higher concentrations of TiO2 and Zr and lower concentrations of Al2O3, Rb, and Ni, and they have higher SiO2/Al2O3 and TiO2/Al2O3 ratios and lower Al2O3/Na2O and Ba/Sr ratios. These features indicate the dust materials of the TJII section were derived from local sources of well-mixed sedimentary protoliths. Our results support the suggestion that paleoclimatic change and the evolution of aeolian sediments were controlled primarily by variation of the East Asian summer monsoon and sea level change.

Emplacement and dewatering of the world's largest exposed sand injectite complex

NASA Astrophysics Data System (ADS)

Sherry, Timothy J.; Rowe, Christie D.; Kirkpatrick, James D.; Brodsky, Emily E.

2012-08-01

Sandstone injectites form by up or down-section flow of a mobilized sand slurry through fractures in overlying rock. They act as reservoirs and high-permeability conduits through lower permeability rock in hydrocarbon systems. The Yellow Bank Creek Complex, Santa Cruz County, California is the largest known exposure of a sandstone injectite in the world. The complex contains granular textures that record processes of sand slurry flow, multiple pore fluids, and dewatering after emplacement. The injection was initially mobilized from a source containing both water and hydrocarbons. The water-sand slurry reached emplacement depth first, due to lower fluid viscosity. As the sand slurry emplaced, the transition from slurry flow to pore water percolation occurred. This transition resulted in preferred flow channels ˜6 mm wide in which sand grains were weakly aligned (laminae). The hydrocarbon-sand slurry intruded the dewatering sands and locally deformed the laminae. Compaction of the injectite deposit and pore fluid escape caused spaced compaction bands and dewatering pipes which created convolutions of the laminae. The hydrocarbon-rich sand slurry is preserved today as dolomite-cemented sand with oil inclusions. The laminae in this injectite are easily detected due to preferential iron oxide-cementation of the well-aligned sand laminae, and lack of cement in the alternating laminae. Subtle textures like these may develop during sand flow and be present but difficult to detect in other settings. They may explain permeability anisotropy in other sand deposits.

Effects of low-scale landscape structures on aeolian transport processes on arable land

NASA Astrophysics Data System (ADS)

Siegmund, Nicole; Funk, Roger; Koszinsky, Sylvia; Buschiazzo, Daniel Eduardo; Sommer, Michael

2018-06-01

The landscape of the semiarid Pampa in central Argentina is characterized by late Pleistocene aeolian deposits, covering large plains with sporadic dune structures. Since the current land use changed from extensive livestock production within the Caldenal forest ecosystem to arable land, the wind erosion risk increased distinctly. We measured wind erosion and deposition patterns at the plot scale and investigated the spatial variability of the erosion processes. The wind-induced mass-transport was measured with 18 Modified Wilson and Cooke samplers (MWAC), installed on a 1.44 ha large field in a 20 × 40 m grid. Physical and chemical soil properties from the upper soil as well as a digital elevation model were recorded in a 20 × 20 m grid. In a 5-month measuring campaign data from seven storms with three different wind directions was obtained. Results show very heterogeneous patterns of erosion and deposition for each storm and indicate favoured erosion on windward and deposits on leeward terrain positions. Furthermore, a multiple regression model was build, explaining up to 70% of the spatial variance of erosion by just using four predictors: topsoil thickness, relative elevation, soil organic carbon content and slope direction. Our findings suggest a structure-process-structure complex where the landscape structure determines the effects of recent wind erosion processes which again slowly influence the structure, leading to a gradual increase of soil heterogeneity.

The Halekulani Sand Channel and Makua Shelf sediment deposits: Are they a sand resource for replenishing Waikiki's beaches?

USGS Publications Warehouse

Hampton, M.A.; Fletcher, C. H.; Barry, J.H.; Lemmo, S.J.; ,

2000-01-01

The Halekulani Sand Channel and the Makua Shelf off the south shore of Oahu contain at least 1.3 million m3 of sediment that is a possible resource for nourishing degraded sections of Waikiki Beach. A sidescan sonar survey indicates continuous sediment cover within the channel and on the shelf, and samples from the top and bottom of vibracores from the channel and shelf contain from 29% to 77% of grains between 0 to 2.5 phi (1 to 0.177 mm), the size range of four samples from Waikiki Beach. Compositional analyses indicate high variability, but the vibracore samples normally have relatively high Halimeda content compared to beach sand samples. Laboratory tests show a positive correlation of abrasion with Halimeda content, suggesting that the offshore sediment would abrade more than beach sediment under nearshore wave action. The common gray color of the offshore sediment can be aesthetically undesirable for sand on popular tourist beaches such as Waikiki; however, visual observation of native beach sand indicates that a significant component of gray color is endemic to many Hawaiian beaches. The gray color was removed in the laboratory by soaking in heated hydrogen peroxide. The geological properties of the offshore sediment indicate potential as a resource for beach nourishment, but industrial treatment might be necessary to remove excess fine and coarse grains, and possibly the gray color. Further, the abrasion potential might have to be considered in calculating beach sand losses over time.

McLaughlin and Mars. [volcanic-aeolian hypotheses for Martian surface features

NASA Technical Reports Server (NTRS)

Veverka, J.; Sagan, C.

1974-01-01

McLaughlin formulated a novel explanation for the Martian albedo markings and their variations. This explanation, the volcanic-aeolian hypothesis, is one of the very few prespacecraft views of planet-wide phenomena on Mars which have stood the test of time. The distribution of albedo markings is considered along with secular changes on Mars and seasonal changes in region Syrtis Major. Mariner 9 has demonstrated that aeolian transport is the dominant factor in determining the distribution of albedo markings on Mars.

Sand Volcano Following Earthquake

NASA Technical Reports Server (NTRS)

1989-01-01

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

Roughness configuration matters for aeolian sediment flux

USDA-ARS?s Scientific Manuscript database

The parameterisation of surface roughness effects on aeolian sediment transport is a key source of uncertainty in wind erosion models. Roughness effects are typically represented by bulk drag-partitioning schemes that scale the threshold friction velocity (u*t) for soil entrainment by the ratio of s...

Interpreting Hydraulic Conditions from Morphology, Sedimentology, and Grain Size of Sand Bars in the Colorado River in Grand Canyon

NASA Astrophysics Data System (ADS)

Rubin, D. M.; Topping, D. J.; Schmidt, J. C.; Grams, P. E.; Buscombe, D.; East, A. E.; Wright, S. A.

2015-12-01

During three decades of research on sand bars and sediment transport in the Colorado River in Grand Canyon, we have collected unprecedented quantities of data on bar morphology, sedimentary structures, grain size of sand on the riverbed (~40,000 measurements), grain size of sand in flood deposits (dozens of vertical grain-size profiles), and time series of suspended sediment concentration and grain size (more than 3 million measurements using acoustic and laser-diffraction instruments sampling every 15 minutes at several locations). These data, which include measurements of flow and suspended sediment as well as sediment within the deposits, show that grain size within flood deposits generally coarsens or fines proportionally to the grain size of sediment that was in suspension when the beds were deposited. The inverse problem of calculating changing flow conditions from a vertical profile of grain size within a deposit is difficult because at least two processes can cause similar changes. For example, upward coarsening in a deposit can result from either an increase in discharge of the flow (causing coarser sand to be transported to the depositional site), or from winnowing of the upstream supply of sand (causing suspended sand to coarsen because a greater proportion of the bed that is supplying sediment is covered with coarse grains). These two processes can be easy to distinguish where suspended-sediment observations are available: flow-regulated changes cause concentration and grain size of sand in suspension to be positively correlated, whereas changes in supply can cause concentration and grain size of sand in suspension to be negatively correlated. The latter case (supply regulation) is more typical of flood deposits in Grand Canyon.

Assessment of sand quality on concrete performance : examination of acidic and sulfate/sulfide-bearing sands.

DOT National Transportation Integrated Search

2014-12-01

The purpose of this research is to examine how the presence of sulfide- and sulfate-containing : minerals in acidic aggregates may affect the properties of mortar and concrete. Analyses were : performed to compare two sands from a deposit in the Geor...

Offshore sand resources for coastal erosion control in Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramsey, K.E.; Penland, S.; McBride, R.A.

1990-09-01

An inventory of existing geophysical data supplemented by more than 15,000 km of high-resolution seismic profiles and 400 vibracores collected cooperatively by the Louisiana Geological Survey and US Geological Survey since 1981 indicates that a wide range of aggregate minerals occurs on the continental shelf in a variety of depositional settings. The distribution of these deposits is controlled by the geometry of the preexisting fluvial and deltaic channel systems and the stratigraphic signature of the Holocene Transgression across these features. The geology of coastal and offshore Louisiana is tied to the depositional history of the Mississippi River. Offshore of themore » delta plain, five types of aggregate sources can be identified: inner shelf shoals, submerged barrier islands, tidal inlets, distributary channels, and barrier platforms. This paper describes the geology of offshore Louisiana, the available geophysical data sets, and the distribution of aggregate mineral resources. On the continental shelf of the Mississippi River delta plain, two extensive seismic survey grids have been developed by the Louisiana Geological Survey and US Geological Survey. The most prospective resources found are the huge sand bodies of Ship Shoal and associated distributaries, Cat Island Pass tidal channels and associated tidal deltas, and Barataria Pass/Grand Terre tidal channels and associated tidal deltas. East of the mouth of the Mississippi River are the Chandeleur Islands, where LGS identified seven major sand resource targets, truncated barrier-spit and tidal inlet deposits, submerged beach ridges, and distributaries associated with abandoned St. Bernard delta complexes. Abundant sand resources can be found in offshore Louisiana. Many of the sand bodies contain heavy minerals, but their concentration and distribution is unknown. Other potential sand resources not yet adequately explored include Sabine Bank, the Outer Shoal, and the St. Bernard shoal.« less

Probe into the origin, development and evolution model of shelf desertizational environment in the last stage of Late Pleistocene

NASA Astrophysics Data System (ADS)

Yu, Hong-Jun; Liu, Jing-Pu; Shan, Qiu-Mei

1998-12-01