Showing papers on "Silt published in 1984"
TL;DR: In this paper, the authors evaluated the usefulness of qualitative descriptors (texture, structure, particle size distribution) as predictors of soil hydraulic behavior and found that the covariation of the hydraulic parameters can be used to construct a classification scheme based on the hydraulic behavior of soils.
Abstract: Stochastic modeling of soil water fluxes in the absence of measured hydraulic parameters requires a knowledge of the expected distribution of the hydraulic parameters in different soil types. Predictive relationships describing the hydraulic parameter distributions must be developed based on the common descriptors of the physical properties of soils (e.g., texture, structure, particle size distribution). Covariation among the hydraulic parameters within these relationships must be identified. Data for 1448 soil samples were examined in an evaluation of the usefulness of qualitative descriptors as predictors of soil hydraulic behavior. Analysis of variance and multiple linear regression techniques were used to derive quantitative expressions for the moments of the hydraulic parameters as functions of the particle size distributions (percent sand, silt, and clay content) of soils. Discriminant analysis suggests that the covariation of the hydraulic parameters can be used to construct a classification scheme based on the hydraulic behavior of soils that is analogous to the textural classification scheme based on the sand, silt, and clay content of soils.
1,451 citations
TL;DR: In this article, a cyclopel is defined as a thin fine-grained sand or silt lamina that grades normally to a thicker poorly to very poorly sorted mud lamina.
213 citations
TL;DR: In this paper, three directional surveys were made in the bore hole from which a deep ice core was obtained in the summers of 1979-81, and the inclination and azimuth were measured on three surveys, fluid pressure and hole diameter on one of the surveys.
Abstract: In 1983 three directional surveys were made in the bore hole from which a deep ice core was obtained in the summers of 1979–81. The inclination and azimuth of the bore hole were measured on three surveys, temperature was included on two surveys, fluid pressure and hole diameter on one of the surveys. Fluid-pressure measurements show that the ice-overburden pressure was undercompensated in the upper few hundred meters and overcompensated at the bottom of the hole. Diameter measurements show closure in the upper portion and expansion near the bottom beginning at the transition from the Holocene to Wisconsin ice at 1784 m. The hole expansion and increase in inclination correlate with dust and silt content in the Wisconsin ice. Changes in azimuth are due to flow of the ice and are consistent with the direction of flow at the surface. Temperature measurements show that the hole is at or near equilibrium. The gradient of 0.012 K/m below 1400 m is less than the 0.018 K/m at Camp Century. There is a slight reduction in gradient near the bottom from internal friction in the silty ice.
100 citations
TL;DR: In this article, the authors investigated the structure, formation and nature of soil crusts which develop as a result of raindrop impact under controlled conditions of simulated rain, and the crust effect on infiltration rates.
85 citations
TL;DR: In this paper, cross-sections were surveyed at straight reaches of 16 sandbed streams in the midwestern U.S. and two stratigraphic horizons were found in the banks at each site, an upper cohesive unit usually composed of silt and clay and a lower unit composed of sand.
Abstract: Cross-sections were surveyed at straight reaches of 16 sandbed streams in the midwestern U.S. Two stratigraphic horizons are found in the banks at each site, an upper cohesive unit usually composed of silt and clay, and a lower unit composed of sand.
Bank erosion on these rivers occurs when the upper cohesive unit is undercut by scour at bends. The overhanging cohesive block fails by toppling forward into the channel. During failure, the soil is primarily in tension rather than compression or shear. Analysis of this failure mechanism leads to a field method for measuring the tensile strength of riverbanks. Measured values of the tensile strength are not correlated with the channel geometry. Thus, the erodibility of the cohesive bank sediments does not influence the geometry of the rivers studied.
72 citations
TL;DR: The use of 14C showed that organisms and metabolic products after incubation of [14C]glucose, existed mainly in larger aggregates (> 250 μm dia), silt and clay sized materials as mentioned in this paper.
Abstract: A mildly leached soil and a calcareous clay soil were dispersed using ultrasound. In the mildly leached soil, organic carbon, nitrogen and ATP (which was used as a guide of the soil microbial biomass) were concentrated in the finer fractions. In the calcareous clay, organic carbon and nitrogen were concentrated in the silt fraction.
When slurries of the same soils were shaken vigourously in a wrist action shaker the soils were more completely dispersed but the recovery of ATP was only 30% compared with 90% after ultrasonic dispersion. It is concluded that the vigorous shaking of a soil slurry is destructive with respect to the biomass and smears cell contents, including ATP, across the colloidal fractions.
The use of 14C showed that organisms, and metabolic products after incubation of [14C]glucose, existed mainly in larger aggregates (> 250 μm dia), silt and clay sized materials. Following physical dispersion the 14C shifted to silt and clay fractions.
It is concluded that while fine clay may be a source of the metabolic products of organisms, the silt fraction a source of cells, and macroorganic matter contains most of the plant debris, the association of microorganisms with inorganic colloids is such that “clean” fractionations of biological components in soils cannot be realized.
64 citations
TL;DR: In this paper, the Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents of the sand, silt, and clay fractions were determined for soils, urban street dust and bottom- and suspended-sediments sampled in the Menomonee River watershed, Wisconsin.
Abstract: The Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn contents of the sand, silt, and clay fractions were determined for soils, urban street dust and bottom- and suspended-sediments sampled in the Menomonee River watershed, Wisconsin. The samples were dispersed by ultrasound prior to fractionation. The ultrasound dispersion avoids chemical contamination or alteration resulting from use of chemical dispersants and insures the dispersion of aggregates present in mechanically-sieved samples.
57 citations
TL;DR: The zonation patterns of shoreline plants vary greatly within lakes and exposure to waves may be an important cause of this variation and a method for ranking lakeshores from low to high exposure was found.
Abstract: The zonation patterns of shoreline plants vary greatly within lakes and exposure to waves may be an important cause of this variation. The principal objective of this study was to find a method for ranking lakeshores from low to high exposure. Two methods for ranking were tried. The first was simply the percent of the substrate composed of silt and clay and the second was calculated based on fetch values from aerial photographs and wind data from a nearby weather station. Field data were collected from 30 points chosen at random along the shoreline of Gillfillan Lake in Yarmouth County, Nova Scotia. Each was sampled for the proportion of silt and clay in the substrate and the zone widths occupied by shoreline plants. Exposure values were calculated for all 30 points, using 16 different methods of calculation. The proportion of silt and clay in the substrate was negatively correlated with exposure, whichever method of calculation was used. Principal components analysis was then used to summarize the zonati...
53 citations
TL;DR: It is suggested that the sediment type, the sediment distribution, the nutritional state of the fish, and the predation pressure influence how sand lance use the sediment as a refuge and how they respond to contamination of that refuge.
Abstract: Sand lance, Ammodytes hexapterus Pallas, forage for zooplankton in the water column and are under heavy predation from fish, marine birds and marine mammals. To avoid predation, these fish bury themselves in soft bottom sediments when not foraging and during overwintering. We collected sand lance in Sequim Bay, Washington State, USA, in 1982. In three experiments we presented the fish with: (1) four different sediment types (fine sand, coarse sand, gravel, silt) to determine their sediment preferences; (2) clean and oil-contaminated preferred sediment to determine whether the fish would avoid the contamination; and (3) clean unpreferred and oil-contaminated preferred sediment to determine whether the contamination would alter their sediment preferences. In the first experiment, sand lance preferred to bury in fine and coarse sands and avoided gravel and silt. In the second experiment, sand lance avoided sand contaminated with Prudhoe Bay crude oil (116 and 1050 ppm). In the third experiment, sand lance avoided the oiled sand (131 and 1041 ppm) and buried in clean gravel, and also avoided both oiled sand (113 and 1004 ppm) and clean silt, and chose to remain in the water column. The sediment particle size and the way it affects water flow through the sediment seemed to be responsible for the preferences. We suggest that the sediment type, the sediment distribution, the nutritional state of the fish, and the predation pressure influence how sand lance use the sediment as a refuge and how they respond to contamination of that refuge.
49 citations
TL;DR: The Eirik Ridge is an 800 km long submarine sediment drift south of Greenland in waterdepths of 2000-3500 m as discussed by the authors, which has been constructed largely by bottom currents formed from cold Norwegian Sea water that overflows across the Denmark Strait.
47 citations
TL;DR: In this paper, the textural characteristics, carbonate content and the coarse fraction components of the Recent bottom sediments of the marine environment off Kuwait are described and the faunal-sediment associations discussed.
Abstract: The textural characteristics, carbonate content and the coarse fraction components of the Recent bottom sediments of the marine environment off Kuwait are described and the faunal-sediment associations discussed. The sediments were subdivided into seven textural classes, namely sand, silty sand, muddy sand, sandy silt, sandy mud, silt and mud. Most of the study area is covered with muddy sediments whereas sandy deposits are restricted to the rocky bottoms near the southern flat of Kuwait Bay, the southern coast of Kuwait and around the islands and bathymetric highs. The textural classes, carbonate contents and faunal types of the coarse fraction were used to construct a biolithofacies map of the marine bottom sediments off Kuwait, in which nine facies are identified. The sedimentological characteristics of the Recent marine bottom sediments off Kuwait reflect the interaction between autochthonous calcareous fragments mostly of biogenic origin, lime rock fragments derived from beachrocks and submerged reef flats, and allochthonous terrigenous detritus transported to the area mainly by dust storms. The Kuwaiti offshore area is generally a low energy depositional environment with little sediment transport.
TL;DR: The Attawapiskat River as discussed by the authors is one of the major low-gradient rivers which cross the flat wetlands of the Hudson Bay Lowland, and it has a nival regime leading to strong, short-duration spring floods during which considerable amount of sediment is carried.
TL;DR: In this paper, chemical weathering and clay mineral formation in basic igneous rocks in the cold desert environment of Antarctica is similar to that of m warmer chmates, where temperatures are sufficiently warm to allow the presence of thin films of salt solution around mineral grains, permitting sufficient moisture to be present for chemical transformation to take place.
Abstract: Chemical weathering taking place in a soil formed on till derived solely from dolerite was investigated. Initially, rock breakdown into smaller particles is by physical weathering. During this process, the ferromagnesian minerals weather chemically, releasing iron and magnesium which recrystallise to form iron-rich montmonllomte In the fine-clay fraction. The silica-rich and chemlcally more resistant minerals accumulate in the silt fraction. Chemical weathering and clay mineral formation in basic igneous rocks in the cold desert environment of Antarctica is similar to that m warmer chmates. These processes can occur whenever temperatures are sufficiently warm to allow the presence of thin films of salt solution around mineral grains, permitting sufficient moisture to be present for chemical transformation to take place
TL;DR: Estimates of invertebrate standing stocks were up to an order of magnitude greater in the present survey, and the variety of organisms was much greater since all types of substrata could be sampled, and there were no indications of increased eutrophication or unusual environmental stress within the study area.
TL;DR: In this article, the hydraulic conductivity of a coarse-textured C horizon at 15 sites was measured in situ with the crust test method, and the data were fit to a simple empirical equation.
Abstract: We measured the hydraulic conductivity of a coarse-textured C horizon at 15 sites. The hydraulic conductivity over the soil water potential range of 0 to - 10 kPa was measured in situ with the crust test method, and the data were fit to a simple empirical equation. The resulting regression coefficients were found to be significantly correlated at the 1% confidence level with the percentage of sand, percentage of silt, bulk density, and porosity of the soil. An equation based only on the sand content of the soil was developed that described 83% of the hydraulic conductivity variation. The equation also successfully described the hydraulic conductivity of a soil with similar physical properties, but was inadequate when applied to a fine-textured soil. The technique shows potential of serving as an easy, reliable, and accurate means for estimating soil hydraulic conductivity.
Journal Article•
TL;DR: In this article, the relationship between texture and microfabric under isotropic stresses generated by wetting and drying is examined by observing and measuring the reorganization of microfabrics (plasmic fabrics and related distribution pattern).
TL;DR: In this paper, seven dust traps were installed across a 100 000 km² region in central and western Texas, and contents of the traps were collected and analyzed at 120-d intervals.
Abstract: As part of a larger study to estimate the impact of airborne dust on pedogenesis, seven dust traps were installed across a 100 000 km² region in central and western Texas. Contents of the traps were collected and analyzed at 120-d intervals. Total annual infall was approximately 12 g/m² with significant seasonal variations occurring. The average clay content is near 60% and is primarily mica and quartz with lesser amounts of smectite and kaolinite. The medium silt (5–20 µm) comprises approximately 25% of the dust and is dominantly quartz with moderate amounts of alkali feldspars. Particulate carbonates were not observed and Ca values for water from the dust traps indicate that if present, carbonates constitute only a small portion of the total infall. Analyses of medium silt grains using SEM and microprobe indicate that quartz and feldspar grains have both smooth conchoidally fractured surfaces and rough pitted morphologies. Grain surface morphology is not adequate for mineralogical identification. Although some materials from local soils may be collected as dust, analyses indicate that the primary source is external to the study area. Grain morphologies suggest multiple source areas for the dust. Substantial uniformity in total infall, particle size distribution, mineralogy, and silt grain morphology was observed across the study area, indicating that the dust depositions are regional in character.
TL;DR: Turnagain and Knik arms, Alaska as discussed by the authors is an extensive sheet of silty sand crossed by tidal channels, exposed at low tide in Turnagain and knik Arms, Alaska.
Abstract: An extensive sheet of silty sand crossed by tidal channels is exposed at low tide in Turnagain and Knik Arms, Alaska. Transportation and deposition of sediment composing this sheet is the result of strong tidal currents due to the maximum spring tidal range of approximately 11.4 m. In Turnagain and Knik Arms, the initiation of the floodtide is accompanied by the occurrence of a tidal bore that travels at a speed of 4 m/sec or more up the tidal channels. In intertidal environments in many parts of the world, physical processes of sedimentation are typically influenced by surface fauna; sedimentary structures in some zones are altered or obliterated by the activities of the infauna. However, in Turnagain and Knik Arms, virtually no macrofauna exist, and so the area provides an opportunity to study depositional processes and sedimentary structures without the masking effects of bioturbation. Suspended-sediment values for Turnagain and Knik Arms are greatest in the summer months and nearest low-tide stages. Ice floes form during winter months and, in combination with the freezing of intertidal sediment to several meters of depth, have a significant effect on sediment dispersal and on the deepening and increased stability of the tidal channels. The intertidal sediment is mainly very well sorted, medium to very fine sand and coarse silt, with a notable paucity of gravel, coarse sand, and clay. Sediment accumulates in sandbars oriented parallel to the axis of the estuary. Textural and facies patterns reflect decreasing current energy, first, as a function of distance from the mouth of the estuary and, second, as a function of topographic elevation on the sandbars. The intertidal deposits in Turnagain Arm contain a transitional upward-fining sequence which is analogous to point-bar and channel-bar successions described by other workers. The base of the sequence contains parallel-laminated sand that is overlain by mixed parallel- and cross-laminated silty sand overlain by cross-laminated silty sand. At the top of the sequence is a unit of organically rich parallel-laminated silt and sandy silt. This suite of sedimentary features and textures indicates changing current velocities and directions as bars emerge or are modified during ebb tide, and the vertical sequences could potentially be used to record intertidal bar erosion and aggradation by point- and channel-bar migration, a process carried out primarily by bed-load currents.
TL;DR: In this paper, a detailed study of the Mississippi River fine-fraction mineralogy was performed using XRD determinations of the mineralogy of suspended sediment collected at three stations across the river during July and November 1980.
Abstract: It has long been known that as a result of frequent deposition the mineralogy of Mississippi River sands remains constant in time and space along the river. There has never been a comparable, detailed mineralogical study of the vastly more abundant muddy sediment of the river. To evaluate the magnitude of variation in Mississippi River fine-fraction mineralogy, suspended sediment was collected at 3 stations across the river during July and November 1980. Samples were disaggregated, and without pretreatment, separated into 4 sizes: 62.5-7.8 µm; 7.8-2.0 µm; 2.0-0.49 µm; and < 0.49 µm. Using calibration curves prepared from pure minerals with an internal standard, XRD determinations of the mineralogy were obtained with a high precision. Minerals quantified were, in order of decreasing abundance: smectite, illite, kaolinite, quartz, plagioclase, alkali feldspar, chlorite, and amphibole. The largest source of variation in suspensate mineral abundance was sediment size. Smectite, for example, comprised 50% of the fine clay, but was not present as silt. ANOVA revealed significant temporal variation in the abundance of smectite and illite within the finest sizes and lateral variation in quartz and feldspar abundance in coarser sizes. Discriminant function analysis determined that the total mineralogy of river-suspended sediment varied significantly with time. This temporal variation in mineralogy apparently results from differences in soil mineralogy in drainage basins of the major tributaries of the river, coupled with t e time-varying contributions of the tributaries.
TL;DR: In this article, the authors examined the ways by which fine sediment may reach the sea bed, and it was shown that gravitational settling through the sublayer dominates over both Brownian diffusion and scavenging by large fast-sinking particles.
Abstract: The ways by which fine sediment may reach the sea bed are examined, and it is shown that gravitational settling through the sublayer dominates over both Brownian diffusion and scavenging by large fast-sinking particles. The settling process is modulated by bed shear stress, which provides a mechanism for preventing deposition of the finest sizes. This allows fractionation during deposition of suspended sediment and may control the amount of silt in a deposit. In contrast, the amount of sand may be controlled by time-winnowing involving removal of the silt and clay fractions.
TL;DR: In this article, the authors used a rainfall simulator to test twenty soils from the Leuven region of Belgium and found significant negative correlations between silt content, aggregate stability, C5-10 index, water content at saturation, and cohesion on the one side and erodibility on the other.
Abstract: Twenty soils from the Leuven region were tested in the laboratory with a rainfall simulator. Their texture varied from loam to loamy sand. On the basis of the results obtained, they were classified as a function of the runoff and splash erodibility. For every soil, several properties were determined and tentatively used to explain the classifications based on the runoff and splash erodibility.
Significant negative correlations were found between silt content, aggregate stability, C5–10 index, water content at saturation, and cohesion on the one side and erodibility on the other; a positive correlation was found between sand content and erodibility.
TL;DR: A general decrease in accumulation rate occurs from proximal to distal regions, and the across-the-shelf maximum rate is in the mid-self region.
Abstract: Accumulation rates (100-yr time scale) in proximal regions of allochthonous dispersal systems range from centimeters to millimeters per year, depending primarily on fluvial discharge of sediment A general decrease in accumulation rate occurs from proximal to distal regions, and the across-shelf maximum rate is in the mid-shelf region Sedimentary structure generally changes from stratified in proximal deposits to homogeneous in distal deposits Although the content of sand and coarse silt commonly decreases along dispersal systems, progressive fining of clay and fine silt is not as obvious Deposition rates (100-day time scale) in proximal deposits can be significantly more rapid (centimeters per month) than longer-term accumulation rates Rapid sedimentation does not necessarily produce mass movement
TL;DR: Shoreline erosion added an annual average of 4 × 106 t of mineral sediment per year to Southern Indian Lake (postimpoundment area, 2391 km2) during the first 3 yr of impoundment.
Abstract: Shoreline erosion added an annual average of 4 × 106 t of mineral sediment per year to Southern Indian Lake (postimpoundment area, 2391 km2) during the first 3 yr of impoundment. This erosion increased sedimentary input to the lake by a factor of 20. The lake retained 90% of this eroded material within its basin, and 80–90% of the retained material was deposited nearshore. Despite the production of extremely fine constituent particle sizes, eroding shorelines generated predominantly large clay aggregates, initially transported offshore as bed load. During bed load transport, abrasion of clay aggregates produced fine particles that became suspended. Over 80% of the suspended load is lost to outflows from the lake because the suspended load is primarily fine silt and clay-sized particles, most of which do not settle even under winter ice cover. The extensive nearshore clay aggregate deposits are temporary, and net deposition in these areas will change to net erosion when input of sediment from eroding shore...
TL;DR: In this article, the chlorite content in the silt fractions by quantitative X-ray diffraction technique was investigated in a Dystric Cambisol and a Placic Podzol.
TL;DR: In this paper, a one-dimensional mathematical model is used to simulate the process of snow-melt infiltration in unsaturated frozen silt, and hydraulic and thermal parameters are mainly based on data given in the model.
Abstract: A one-dimensioinal mathematical model is used to simulate the process of snow-melt infiltration in unsaturated frozen silt. Hydraulic and thermal parameters are mainly based on data given in the li ...
TL;DR: In this article, an instability analysis was made with respect to the seepage conditions in the weathered limestone layer which might have been altered due to the increase in pore water pressure in the upperlying alluvial sand deposit during the Vrancea earthquake.
TL;DR: A three-dimensional model for a tidal inlet-barrier island depositional system was constructed through examination of 37 vibracores and 10 auger drill holes on Capers and Dewees islands, South Carolina.
Abstract: A three-dimensional model for a tidal inlet-barrier island depositional system was constructed through examination of 37 vibracores and 10 auger drill holes on Capers and Dewees Islands, South Carolina. Two cycles of southerly inlet migration and subsequent abandonment resulted in beach ridge truncation on the northern ends of both barriers. Historical evidence indicates that these tidal inlets migrated 1.5 km to the south owing to a dominant north-south longshore transport direction. The hydraulic inefficiency of these over-extended inlet channels caused shorter, more northerly-oriented channels to breach through the ebbtidal deltas. After inlet reorientation, large wave-formed swash bars migrated landward closing former inlet channels. Weakened tidal currents through the abandoned channels permitted clay plugs to form thick impermeable seals over active channel-fill sand and shell.
Price and Capers Inlets formed during the onset of the Holocene transgression following submergence of the ancestral Plio-Pleistocene Santee River drainage system. Coarse, poorly sorted inlet-deposited sand disconformably overlies Pleistocene estuarine clay and is capped by a dense clay plug. Shoreline reorientation and landward retreat of a primary barrier island chain occurred between the first and second cycles of inlet-channel migration and abandonment. Beach ridges prograded seaward over the first inlet sequence. A second cycle of inlet migration truncated the northernmost portion of these beach ridges and scoured into the clay plug of the earlier inlet deposit. Abandonment of this channel resulted in deposition of a second abandoned inlet-channel clay plug. Abandoned tidal inlet channels exhibit U-shaped strike and crescentic- to wedge-shaped dip geometries. Basal, poorly sorted inlet sands are sealed beneath impermeable, abandoned-channel silt and clay, washover deposits, and salt marsh. Multiple episodes of inlet migration and abandonment during a rising sea-level deposited stacked inlet-fill sequences within the barrier islands.
The resultant stratigraphy consists of interlayered, fining-upward, active inlet-fill sand overlain by thicker abandoned inlet-fill clay plugs. These clay plugs form impermeable zones between adjacent barrier island sand bodies. Shoreline transgression would remove the uppermost barrier island deposits, sealing the inlet-fill sequences between Pleistocene estuarine clay and shoreface to shelf silt and clay.
TL;DR: In the case of the floodplain of the Ohio River, the sedimentation rate decreased and the sand content of the sediments diminished, and as the river channel occasionally shifted, the ridged deposits were built in successive subparallel sequences as mentioned in this paper.