Showing papers on "Silt published in 1971"

Soil erodibility nomograph for farmland and construction sites

Abstract: A NEW SOIL PARTICLE-SIZE PARAMETER WAS FOUND AND USED TO DERIVE A CONVENIENT ERODIBILITY EQUATION THAT IS VALID FOR EXPOSED SUBSOILS AS WELL AS FARMLAND. A SIMPLE NOMOGRAPH PROVIDES QUICK SOLUTIONS TO THE EQUATION. ONLY FIVE SOIL PARAMETERS NEED TO BE KNOWN: PERCENT SILT, PERCENT SAND, ORGANIC MATTER CONTENT, STRUCTURE, AND PERMEABILITY. THE NEW WORKING TOOL OPENS THE DOOR TO SEVERAL NEW CONSIDERATIONS IN SEDIMENT- CONTROL PLANNING. /AUTHOR/

Slumping on a Continental Slope Inclined at 1o-4o

Abstract: Continuous seismic profiles from the upper continental slope east of North Islands, New Zealand, show that surface sediment 10–50 m thick has slumped down bedding planes sloping at 1°–4°. There are four slumps, the Kidnappers Slump which has an area of 250 km2, the Paoanui Slump of 80 km2, a small slump of only several square kilometers and a slump of undetermined extent. All occurred during the last 20,000 years in Last Glacial Age sediments. A glide plane is exposed at the head of each slump and beds are thrust or contorted at the toe of some slumps. Slumping was probably caused by the failure of loosely packed sandy silt during major earthquakes.

Classification of Fine-grained Sedimentary Rocks

Abstract: Classifications of fine-grained sediments and sedimentary rocks are based on combinations of several criteria. These include: (1) texture, (2) fissility, (3) tectonic association or environment of deposition, (4) mineral composition, (5) color, (6) chemical composition and (7) degree of metamorphism. None of the classifications are generally used, however. For field studies, texture is the most significant property. The proportions of clay, silt and sand are used herein to define four major groups: claystone (clay), siltstone (silt), mudstone (mud) and sandstone (sand). Claystone, siltstone and sandstone are rocks containing more than 50 percent of clay-, silt- or sand-sized material, respectively. Mudstone contains less than 50 percent of clay, slit or sand. Silty and sandy are useful modifiers of claystone when clay-sized material is less than 75 percent but more than 50 percent. Clayey and sandy are used to modify siltstone when silt-sized material is less than 75 percent but more than 50 percent. The expression good sorting is applied to fine-grained clastic rocks that contain more than 90 percent silt or clay-sized material. Fair-sorted rocks contain 75 to 90 percent silt or clay. Poorly sorted siltstone or claystone contains less than 75 percent silt or clay. If fissile, fine-grained clastic rocks are so designated. The mineral composition of most fine-grained clastic rocks can be determined reliably with the petrographic microscope and by X-ray diffraction. Therefore, where possible, they should also be named according to one of the sandstone classifications and on the dominant clay mineral present. Color, bedding types and sedimentary structures, fossil content, type of cement and fissility should be included in complete descriptions. An example of a good field and laboratory description is: clayey siltstone, illite-subarkose, poor sorting, grayish red (5R4/2), dolomite cement, slabby, horizontal lamination, pelecypods.

Negative skin friction for long piles driven in clay

Abstract: THE LOAD DISTRIBUTION IN TWO INSTRUMENTED PRECAST CONCRETE PILES WHICH HAVE BEEN DRIVEN THROUGH 40 M OF CLAY, 13 M OF SILT, AND 15 M OF SAND IS DESCRIBED. THE LOAD IS CAUSED BY NEGATIVE SKIN FRICTION DUE TO RECONSOLIDATION OF THE REMOLDED CLAY AROUND THE PILES AFTER DRIVING. THE SOIL CONSISTS AT THE TEST SITE OF HOMOGENEOUS NORMALLY CONSOLIDATED CLAY WITH A WATER CONTENT OF AROUND 80 PER CENT AND AN UNDRAINED SHEAR STRENGTH AT THE SURFACE OF ABOUT 2 TONS/M SQUARE AND 7 TONS/M SQUARE AT THE DEPTH OF 40 M. PIEZOMETERS AND SETTLEMENT GAGES WERE INSTALLED IN THE SOIL PRIOR TO THE DRIVING. A NEW, ACCURATE PILE-FORCE GAGE HAS BEEN DEVELOPED FOR THIS PROJECT, WHICH MAKES IT POSSIBLE TO MEASURE THE LOAD AND THE MOMENT DISTRIBUTION IN A PILE AFTER DRIVING. MEASUREMENTS SHOWED THAT THE LOAD IN THE PILE IMMEDIATELY AFTER DRIVING WAS ROUGHLY EQUAL TO THE WEIGHT OF THE PILE ITSELF. DURING THE FIVE-MONTH PERIOD FOLLOWING THE DRIVING, THE LOAD IN THE PILE INCREASE BY ABOUT 30 TONS AT THE BOTTOM OF THE CLAY LAYER. THIS LOAD INCREASE CORRESPONDS TO A NEGATIVE SKIN FRICTION WHICH INCREASES LINEARLY FROM 0 AT THE GROUND SURFACE TO ABOUT 1.4 TONS/M SQUARE AT THE BOTTOM OF THE CLAY LAYER. THE NEGATIVE SKIN FRICTION IS EQUAL TO 17 PER CENT OF THE UNDRAINED SHEAR STRENGTH OR TO 5 PER CENT OF THE AVERAGE EFFECTIVE OVERBURDEN PRESURE. /AUTHOR/

Loess in the soils of north norfolk

Abstract: Summary Thin silty deposits cover large areas of north-east Norfolk, occurring mainly on gently sloping and flat plateau sites and on the floors of valleys cut in the glacial deposits. Particle size and geographic distribution of the deposits suggest that the silt is windblown. The mineralogical composition of the silt fraction resembles that of the silt of Hunstanton Till, suggesting that most of the deposit was derived as loess from outwash of the Weichselian glacier. However, at some localities the sand and clay components of the deposits were derived, at least partly, from subjacent glacial sediments of pre-Weichselian age. The distribution of the silty deposits strongly affects the pattern of soil types and sometimes the growth of crops.

Mineralogy of sediments in three Georgia estuaries

Abstract: Mineralogical analyses of suspended sediments and bottom sediments from three Georgia estuaries (Altamaha, Ogeechee, and Satilla Rivers) indicate that the clastics of this area are a mixture of fluvially derived Piedmont and Coastal Plain detritus, and fines derived from the continental shelf. High illite-montmorillonite clay suites are transported into the estuaries from offshore during flood tide, whereas kaolinite plus minor mixed-layer clay, vermiculite and talc from the Piedmont and montmorillonite from the Coastal Plain and/or paralic sediments characterize the upstream and intermediate areas of mixing within the estuaries. Decreasing flow velocity and flocculation of the clays, probably induced by salinity changes, results in a general change in bottom sediments from sand in th rivers to clay in the estuaries. Sands and silt fractions are high in quartz with significant amounts of feldspar in the Altamaha (Piedmont source). Heavy-mineral composition of these sediments reflects the proportionality of the division of the drainage basins between the Piedmont and the Coastal Plain. The former is characterized by unstable suites, whereas the latter contributes stable to ultrastable assemblages. Sorting is generally poor reflecting a variety of processes which influence the sediments within the estuary. The work amplifies the conclusions of previous workers that shoreward transport, especially for the fine fraction, is an important process in determining the composition of the estuarine sediments.

Deltaic Sedimentation in Athabasca Tar Sands

Abstract: The Athabasca tar sands of northern Alberta underlie an area greater than 26,000 sq km and contain more than 700 billion bbl of heavy oil. Excellent outcrops of the oil-impregnated Lower Cretaceous strata (McMurray and Clearwater Formations) are present in the valley of the Athabasca River and its tributaries near Fort McMurray. The middle and upper members of the reservoir consist of many small deltas of limited thickness (less than 30 m) built by rivers flowing northward into a lake or lagoon. The water occupied an elongated depression formed by extensive salt removal from evaporite beds beneath the Devonian limestone which underlies the tar sands. Lithofacies associated with the changing environments of deposition during the infilling of this depression include, succes ively, fluvial sand; delta-front sand and silt; deltaic-platform sand, silt, and clay; and nearshore marine sand. The distribution of oil within the tar-sands reservoir is strictly controlled by the original porosity and permeability of the sediments. Thus, the maximum amount of oil (18-20 percent by weight) is present in well-sorted, clean sands that are most commonly of fluvial origin. No oil is present in the poorly sorted, argillaceous parts of the nearshore marine sands, or in the silt beds within the deltaic complex.

Grand Isle: A Barrier Island in the Gulf of Mexico

Abstract: Grand Isle is a barrier island composed entirely of sediments, most of which are terrigenous. Surface sediments of the island are primarily fine- to very fine-grained sand, some silt and with some clay. The sand fraction is basically quartz but contains 18.7 percent feldspar. Size characteristics of the sediments parallel geomorphic features such as the beach, dune, back-island ridges, and inter-ridge areas. Silt and clay fractions of the sediment generally increase behind the dune complex of the island. This finer fraction is interpreted as being secondarily introduced from the bay-sound environment by influxes of high water and by aeolian transport. Sorting coefficients closely parallel geomorphic features of the island. Median grain-size diameters for the island range downward from 0.166 mm. Two factors indicate that beach material moves into the Grand Isle area via littoral currents from the southwest: (1) all grain-size characteristics of beach material increase to the southwest; and (2) sediment buildup occurs on the southwest sides of the jetty and groins. Organic content of the sediment is lowest in environments of high physical energy and high oxidation, and these generally parallel geomorphic features. Approximately 25 sets of relict beach and dune ridges are present behind the active beach and dunes. The orientation of these low relief back-island features indicates that the island has grown at its distal ends and seaward by accretion. The Holocene-Pleistocene contact is at approximately 400 ft below the surface at Grand Isle. Four sands are present in the Holocene column, these are interlayered with clay and silty clay. The upper two sands have a linear configuration and are as much as 43 ft thick. The deepest sand is more than 120 ft thick. Subsurface strata studied at Grand Isle are related to the Holocene marine transgression and the Mississippi River deltaic progradation. Holocene sediments of Grand Isle are 20,000 yrs old or less. The “D” Sand (at about 200 ft below sea level) was deposited during the Holocene marine transgression. The “C” Sand was deposited as a nearshore Gulf deposit. The “A” and “B” Sands were deposited as barrier islands or barrier island spits. The two uppermost sand bodies are less than 1000 yrs old. The “A” and “B” Sands were deposited by northeasterly moving littoral currents which flow contrary to the prevailing longshore currents. The oldest, continuously subaerial, segment of the present island is interpreted to be less than 700 yrs old. The island probably originated as a barrier spit which extended northeastward from the Lafourche delta front. The barrier spit waspossibly separated from the mainland by a tidal current breakthrough or surge of storm waters. Since separation from the mainland, the island hasgrown to each end, and seaward, by ridge accretion.

Turbidites of the northeast pacific1

Abstract: The northeast corner of the Pacific Ocean is a region of turbidity-current activity. Cores from this area are dominated by very fine-grained sand and medium-grained silt that grade upward to clay. The results presented in this article are based on 217 textural analyses of turbidite layers comprising 30 piston cores. It is possible to distinguish proximal and distal facies of turbidites using characteristics of layering, grading and texture. Features of the proximal facies include wide range of layer thickness, maximum layer thickness, non-grading, truncation of grading, textural reversals, and sand at the base of graded layers. Areas beyond main routes of submarine flows are sites of episodic addition of silt-through clay-sized sediment. The proportion, thickness, and mean grain size of the silt decreases with increasing distance from the main avenues of flow.

Stress-strain behavior of frozen fine-grained soils

Abstract: THE OBJECTIVE WAS TO INVESTIGATE THE EFFECT OF BELOW-FREEZING TEMPERATURE, CONSTANT AXIAL DEFORMATION RATES, AND SOIL TYPE ON THE STRESS-STRAIN BEHAVIOR AND STRENGTH OF FROZEN FINE GRAINED SOILS. TWO SOILS WERE SELECTED: A HIGHLY PLASTIC CLAY AND A CLAYEY SILT. SAMPLES WERE CORED OUT OF STATICALLY COMPACTED SOIL CAKES AND QUICKLY FROZEN. AVERAGE MOLDING DENSITIES AND AVERAGE MOLDING WATER CONTENTS OF TEST SAMPLES FELL ON THE WET SIDE OF OPTIMUM CONDITIONS DETERMINED BY STANDARD PROCTOR CURVES OF COMPACTION. CONSTANT AXIAL DEFORMATION RATE TESTS WERE CARRIED OUT ON FROZEN SAMPLES AT -1, -5, -9, AND -22 C, AND AT DIFFERENT CONSTANT AXIAL DEFORMATION RATES. TWO TYPES OF STRESS-STRAIN BEHAVIOR WERE EXHIBITED; THE BRITTLE TYPE WAS ASSOCIATED WITH THE CLAYEY SILT, AND THE PLASTIC TYPE WAS ASSOCIATED WITH THE CLAY. RESULTS ALSO SHOW A STRONG DEPENDENCY OF ULTIMATE STRENGTH (PEAK STRENGTH) DERIVED FROM STRESS-STRAIN CURVES ON TEMPERATURE FOR BOTH SOILS TESTED. ULTIMATE STRENGTH IS ALSO SHOWN TO DEPEND ON DEFORMATION RATE. THE INFERENCE MAY BE DRAWN THAT THE AMOUNT OF LIQUID WATER PRESENT AS A THIN FILM BETWEEN SOLID AND ICE SURFACES AND THE RATIO OF LIQUID WATER TO ICE IN A FROZEN SOIL ARE RESPONSIBLE FOR ICE CEMENTATION BONDS. THESE BONDS IN TURN CONTROL THE STRESS-STRAIN BEHAVIOR AND THE ULTIMATE STRENGTH OF FROZEN SOILS. /AUTHOR/

Control of slope on deposition from small‐scale turbidity currents: experimental results and possible geological significance

Abstract: The experiments involved pouring aqueous starting suspensions of pumice sand and kaolinite silt into a submerged trough. The steepness of the bottom slope of the trough was varied from run to run. Heights of sand and silt were recorded at 10-cm intervals away from source. The results: (1) support earlier suggestions that the ratio of sandstone to shale is a sensitive indicator of proximality in ancient turbidites, but do not support clearly the suggestion that the rate of decrease in that ratio away from source may indicate steepness of bottom slope; (2) suggest that the rate of decrease in sandstone thickness away from source in ancient turbidites may be inversely proportional to steepness of bottom slope. The possible application of the results to the geological record is discussed.

Relations among radionuclide content and physical, chemical, and mineral characteristics of Columbia River sediments

Abstract: Ml Presentation of data Continued Introduction 2 Mineralogy Continued Sample collection and preparation 3 Silt (size classes 7, 8, and 9) ......... ..M27 Analytical procedures 6 Discussion: Quantitative X-ray mineralAcknowledgments .. .... 7 ogy..... .... .. . 31 Presentation of data 8 Sand (size classes 2-6) and gravel (size class Cation-exchange capacity........-.-....-.......-.--.-..-... 8 l),by R. 0. Van Atta . ........ 32 Nitrogen and carbon content... 12 Radionuclide content ...... 36 Mineralogy......... 14 Interpretation of radionuclide data 45 Clay (size class 11) 14 Conclusions ........ 49 Silt (size class 10) ...... .... . ......... 21 References cited ...., 51

Factors Affecting Mass Movement of Four Soils in the Western Cascades of Oregon

Abstract: Four soils derived from tuffaceous rock in the Western Cascades were studied to determine relationships to slope stability. Two of the soils derived from greenish tuff and breccia were prone to slope failure. The other two soils were derived from yellowish and reddish tuff and breccia and were more stable. Soils prone to slope failure were characterized by high amounts of smectite clay, absence of kaolin, and moderate amounts of free iron oxide. The more stable soils contained kaolin, more chlorite and chloritic intergrades, less smectite, and higher amounts of free iron oxide. Pseudomorphs of clay were the major component of silt and sand fractions. The pseudomorphs seem to function mechanically as primary soil particles but the clay contributes to cation exchange and moisture retention. The ratio of clay calculated from 15-bar moisture retention to measured clay was highest for the most stable soils. Stability of these soils did not appear to correlate with clay content, content of amorphous clay, or proportions of exchangeable cations. Color of the soils and of their source rocks was correlated with clay mineralogy, content of iron oxides, and landscape stability.

Highly calcareous lacustrine soils in the Great Konya Basin, Turkey

Abstract: The Great Konya Basin is in the south of the Central Anatolian Plateau in Turkey. It is a depression without outlet to the sea. The central part of the Basin is the floor of a former Pleistocene lake, the Ancient Konya Lake. This area, called the Lacustrine Plain, has highly calcareous clayey sediments and is flat and level, except for ancient shorelines which form sandy ridges and beaches. Its soils have been studied in the summers of 1964-8 as part of the Konya Project, a research and training programme of the Department of Tropical Soil Science of the Agricultural University, Wageningen. This book is the last publication about the results in a series of five. The Quarternary history of the Lacustrine Plain, as regards sedimentation, was reconstructed with the help of existing climatic chronologies and with observations on geomorphology, soils, shells and pollen. Presumably Ancient Konya Lake, which had a constant level of about 1017 m, dried up in Postpluvial I (about 16.000 BC) and four smaller lakes or marshes existed in secondary depressions during Sub-pluvial I (about 9000 BC) which gradually disappeared. Their level varied between 1000 and 1006 m. The soils of the Lacustrine Plain were mostly formed in white uniform carbonatic clay, but differ markedly in composition and morphology because of past and present differences in hydrology, topography and vegetation. The soils have been studied and mapped on a regional basis and divided into Steppe Marl Soils, Marsh Marl Soils and Playa Marl Soils. The last group occurs north and east of Karapinar and is strongly salt- affected. Profile data of some 13 representative Marl Soil profiles are presented in the form of structural diagrams and tables for easy reference. Soil peels (preserved natural soil profiles) of the same representative soils are also used for a precise description of the pedological features and voids of the soil material, using Brewer's system of 'pedography'. Areas for more expensive thin sections could be selected more carefully. Interpretation is based on the descriptions in the field, in the soil peel and occasionally in thin section. Organisms, presumably mainly earthworms, seemed the main cause of the present structure of the solum. The effects of recent cultivation and irrigation are also demonstrated. Redistribution of carbonates humus and iron is observed and explained. The textural and mineralogical composition of Marl Soils was studied superficially. The soil texture without removal of carbonates is mostly clay to silty-clay and is slightly finer- textured after carbonates have been removed. The carbonates (mainly calcium carbonate as calcite) occupy about an equal proportion of the clay, silt and sand fractions. Clay minerals of the smectite group are commonest and palygorskite is present. The carbonatic clayey parent material of the Marl Soil is a sediment of about 60% mainly chemically precipitated calcite, debris from limestone and shells and the rest is a residue of non-calcareous clay minerals of residual and alluvial origin and sand sized mineral grains of alluvial or aeolian origin. The productivity of Steppe Marl Soils is estimated, using results from the soil peels and data on moisture and soil fertility. The suitability for agriculture is estimated by an existing procedure, which was refined and adapted to the area. The procedure compares estimated deficiencies in soil structure, soil moisture and chemical soil fertility in comparison with ideal conditions. The feasibility for improvement is then assessed for three management systems: dry farming without fertilizers, dry far ing with fertilizers and irrigated farming with fertilizers. The soil suitability in 4 classes (good, fair, restricted and unsuitable) is assessed on the basis of the above analysis. The suitability of Steppe Marl Soils for agriculture is judged as 'unsuitable' or 'restricted' under the dry-farming systems, mainly because of lack of moisture and 'restricted' under irrigation (mainly because of poor irrigability and poor response to fertilizers). It may become 'fair' under highly sophisticated irrigational management as is demonstrated on comparable soils in Israel and Florida.

The 'Sawdust Sand'; an Eocene sediment of floccule origin

Abstract: The "Sawdust Sand" of the Eocene-Wilcox in western Tennessee is an unconsolidated sediment composed largely of aggregate grains. The aggregate grains and cross-stratification give the "Sawdust Sand" the appearance of medium to coarse, well-sorted sands. When disaggregated the sands become poorly sorted, silty and clayey, very fine sands, indicating a break-down of the aggregate particles. Two general types of aggregates are present: those composed chiefly of clay mineral particles in a three dimensional array of face to face (FF), edge to edge (EE) and edge to face (EF) configurations; and those where silt and fine sand-sized quartz and feldspar are included in the clay mineral particle network. The aggregates have clay mineral compositions of kaolinite-montmorillonite or kaolinite and the two mineralogical suites are stratigraphically segregated. The fabrics and textures of the aggregate grains, their mineralogical associations and their primary stratification lead to the conclusion that the aggregate grains in the "Sawdust Sand" are relict floccules.

Heredity and Environment in Clastic Sediments: Silt/Clay Depletion

Abstract: The mechanical composition of clastic deposits is usually compared either with an ideal statistical distribution or with the postulated end product of a particular depositional environment. It would seem preferable to employ the parent material as the standard of comparison since it determines the range of grain sizes potentially accessible to its daughter deposits. This approach is practicable in the Mediterranean area and Iran, where many valleys contain two alluvial fills of which the younger consists largely of material derived from the older. Relative silt/clay depletion of the younger fill suggests that, although the parent deposit was laid down by intermittent floods, the second phase of aggradation was characterized by sustained flow during which suspended load could leave the basin preferentially.

Effect of Mica on K O Compressibility of Two Soils

Abstract: The effect of mica content on the compressibility of a sand and a silt under conditions of zero lateral yield consolidation was investigated. The sand tested was the medium, uniform, subangular Chattahoochee River sand, and the silt was a residual soil from the Atlanta, Georgia area. A special lateral deformation sensor was designed to be placed on a triaxial test sample and limit the lateral deformation to less than 0.001% Mixtures of from 0% to 50% mica in sand and 0% to 50% mica in silt were tested. The results of the sand series showed that for a given initial void ratio the compressibility was significantly increased by the addition of a small amount of mica, but K O was not affected. For the silt series, partially saturated samples were formed under light static compaction. The results of the series showed no significant effect of mica content on the compressibility; however, there was a tendency for an increase in the coefficient of earth pressure at rest with increasing mica content.

Soils of the Savannah River Project, Aiken, South Carolina

Abstract: The author mapped and evaluated soils of the Savannah River Project for management. The Author mapped the soils of the Savannah River Project area and evaluated their suitability for various management activities. The latter included forestry and industrial uses. In general the soil of the Savannah River Project area are representative of the sandhills and upper coastal plain geological complex. Soils in the uplands are dominated by sand overlying clays that are suitable for pine management. Soils in the area adjacent to the Savannah River are the most biologically productive and consist of heavy clay and silt deposition. The project provided a common nomenclature for soil mapping consistent with the SCS Survey Procedures

Limnogeological Studies of the Eastern Part of the Lake Superior Basin

Abstract: The topography of the lake-bottom between St. Mary's River and Michipicoten Harbour (Lake Superior, Ontario), consists of a lake-shelf, 2 to 4 miles (3.2–6.4 km) wide, and a series of north–south aligned topographic deeps and highs, 3 to 4 miles (4.8–6.4 km) wide, lakeward. This topographical trend is in marked contrast to the east–northeast and east–southeast trends of the onshore Precambrian rocks.The Holocene sediments of the lake-bottom consist of sand, which covers the lake-shelf and topographical highs, and clay-silt which covers the topographical deeps. The sands of the lake-shelf area can be differentiated from the sands of the topographical highs on the basis of grain-size parameters and mineral composition. The clay-silt sediments of the topographical deeps form the following consistent stratigraphic sequence: an upper, thin veneer of dark yellowish brown silt; an intermediate unit of olive gray, fine-grained silt to coarse-grained clay; and a lower unit of dark yellowish brown silt. These Holoc...

Effect of Physical and Chemical Properties on the Erodibility of Some Soils of the Malwa Plateau

Abstract: The influence of physical and chemical properties on the erodibility of some soils of the Malwa plateau in Madhya Pradesh was investigated. Erosion ratio was negatively correlated with clay/(silt + sand) ratio, percentage of water stable aggregates larger than 0.25 mm, percentage of exchangeable calcium in the soil, and silica-iron oxide ratio. Highly significant positive correlations were obtained between erosion ratio and the percentage of volume expansion, and between erosion ratio and moisture equivalent. A linear regression equation relating the erosion ratio to clay/(silt + sand) ratio, moisture equivalent, and the percentage of calcium carbonate is described to estimate erosion ratio in these and similar soils.