Sorting Coefficient Research Articles

Empirical Relations in Properties of Unconsolidated Quartz Sands and Silts Pertaining to Water Flow

During a laboratory investigation using radiotracers, empirical formulas were developed to replace the ambiguous or incorrect Dupuit‐Forchheimer assumption used in relationships governing the flow of water through porous, unconsolidated materials ranging from clay to coarse sands or fine gravels. The Dupuit‐Forchheimer assumption states that the ratio of specific flow rate to average flow velocity is equal to porosity, but it is not specified whether true porosity or void ratio or specific yield, also called effective porosity, is meant. The hydraulic conductivity shows a good correlation with the maximum 10% grain size, and the ratio of specific flow rate to average flow velocity shows good correlation with functions of specific yield and percentile sorting coefficient. From field measurements of specific flow rate and average flow velocity the specific yield can be computed.

THE IDENTIFICATION OF ANCIENT BEACH SANDS BY THE COMBINATION OF SIZE ANALYSIS AND ELECTRON MICROSCOPY

SUMMARYThe combined use of size analysis and electron microscopy has indicated the presence of beach sands within the Lower Carboniferous Fell Sandstone of southeast Scotland and northern England.Environmental interpretations are based on a comparison of the statistical parameters summarizing the size distributions of the Fell Sandstone specimens with similar data from modern sediments. The spread of standard‐deviation values (sorting coefficients) indicates the presence of littoral, alluvial, and possibly offshore marine environments within the Fell Sandstone. These environments are further defined by plotting standard deviation against skewness on a scatter diagram.Electron micrographs (E.M.G.'s) of the quartz grain surface textures of selected Fell Sandstone specimens corroborate the interpretations based on the size analysis.E.M.G.'s of the Fell Sandstone beach specimens show all the diagnostic surface features developed on modern quartz beach sand grains.

Preliminary sedimentological evaluation of some flysch-like deposits from the Makara Basin, Central Hawke's Bay, New Zealand

Abstract Samples of flysch-like deposits from the Middle Tertiary Makara Basin, Central Hawke’s Bay, show a frequency grading for cycles of sandstone and their overlying siltstone beds. That is, the mean grain size decreases upwards, whereas the maximum grain size remains the same. Statistical parameters, introduced by Folk and Ward (1957), indicate that the samples are poorly to very poorly sorted and are positively skewed. Frequency distributions are truncated at or between 250 and 500 microns. Sandstones are leptokurtic or very leptokurtic, whereas the siltstones are platykurtic. The sorting measure of Folk and Ward is shown to be superior to Trask's sorting coefficient for skewed sediments. The grain size distributions are not lognormal, probably due to the polymodal character of the sediments. If only the size fractions finer than 125 microns are considered, the distributions approach arithmetic normality. Data from some Recent sediments are compared with those of the Makara samples. Plotting of the Makara samples in a CM-diagram gives a pattern thought to be characteristic of sediments deposited by tractive currents.

Estudo dos materiais calcários usados como corretivo do solo no Estado de São Paulo: I - Composição granulométrica

São apresentados dados sôbre a composição granulométrica de calcários e escória de alto forno, usados como corretivos do solo. O ensaio granulométrico foi efetuado por tamisação, para o que foram usadas 9 peneiras, de n.° 10 a 2002. A maior parte das amostras apresentaram composição granulométrica semelhante. Cêrca de 20% a 30% das partículas apresentaram diâmetros entre 0,8 mm a 2,0 mm, e cêrca de 25% a 35%, diâmetros inferiores a 0,15 mm. Os resultados indicam que as amostras apresentam seleção máxima na parte mais grosseira. Na maioria delas, essa fração está representada por partículas de diâmetro maior que 0,3 mm, em proporção que varia de 50% a 60%.

EXPERIMENTS ON DENSITY AND TURBIDITY CURRENTS: III. DEPOSITION OF SEDIMENT

Turbidity currents were formed by releasing suspensions of plastic beads (density 1.52, median diameter 0.18 mm) from a lock into a horizontal water-filled flume. Graded beds were formed; the mechanism of deposition was studied by motion photography and the size grading by 150 size analyses.Deposition of sediment took place behind the head even at a time when there was no deceleration of the head: the greater part of the thickness of the bed was deposited during a period of rapid decline in velocity of flow within the body of the current. The mechanism of deposition and the type of grading differed for beds deposited from suspensions with concentrations less than and greater than about 30% by volume. Low concentration suspensions formed 'distribution grading' in which all percentiles showed vertical grading and at least the coarser half of the distribution showed lateral size decrease away from the gate. High concentration suspensions formed 'coarse-tail grading' in which there was almost no lateral size variation and the vertical grading was shown only by the coarsest few percentiles (except at the top of the bed).In high concentration flows the bed did not accumulate layer by layer, as it did in low concentration flows, but was deposited first as an expanded 'quick' layer, which was deformed by shearing and waves produced by the entrained water flowing over the still plastic bed.In both types of graded beds the sorting coefficient (standard deviation of the logarithm of the settling velocity) decreased upward within the bed, and to a lesser extent also laterally away from the gate. The skewness reached a maximum near the center of the bed and became negative at the top.

Evolution of Part of the Lower Critical Zone, Farm Ruighoek, Western Bushveld

This study of a part of the lower Critical Zone, Farm Ruighoek, Western Bushveld, is based mainly on selected drill core samples from two sections approximately 1.2 miles apart. The 1300-ft sequence investigated consists of pyroxenites with two harzburgite bands and sixteen chromitite seams. Results obtained are consistent with the hypothesis that evolution of the sequence was a cyclic process in which cumulate minerals crystallized in a zone near the floor of accumulation under generally quiescent conditions. Compositional changes of cumulate minerals reflect the influence of a separate intrusion of undifferentiated parent magma or refusion at depth of crystals formed near the top of the magma chamber. Interstitial mineral content and plagioclase composition reflect changing rates of crystal accumulation. Orthopyroxene grain size and sorting coefficient reflect, in part, the vertical distance over which crystallization occurred. Textural features and contact relations of chromitite seams are consistent with the hypothesis that most chromite crystallized from the silicate magma and accumulated during a period of little or no crystallization of silicate minerals. It is postulated that this loose crystal assemblage was enriched by co-accumulation and partial in situ crystallization of chromite-rich immiscible liquid. Textural, mineralogical, and compositional changes in footwalls and hanging walls of chromitite seams are thought to reflect in situ reactions.

Textural Comparison of John Day Volcanic Siltstone with Loess and Volcanic Ash

ABSTRACT Rocks of the John Day Formation (middle Oligocene-lower Miocene) in eastern Oregon are composed of fragments derived from volcanic vents and include air-fall tuff, fluvial tuff, lacustrine tuff and ignimbrite. The majority of the John Day rocks, however, are massive tuff that resemble loess deposits. The median diameters and sorting coefficients of these rocks are similar to both loess and fine-grained volcanic ash, but plots of a ratio using median diameter and sorting coefficient ([Md]/[Md + ]) suggest that the massive John Day rocks are most like air-fall tuffs. Their resemblance to wind-raised and wind-deposited loess deposits is attributed to soil-forming and soil-mixing agents that operate during the slow deposition of dust; namely, frost-heaving, plant-wedging and soil-living animals. The interpretation that these massive rocks are mainly air-fall tuff is commensurate with paleobotanical evidence that suggests a warm temperate climate, rather than a dry climate that could produce dust storms necessary to deposit several hundred feet of structureless volcanic dust.

Some Aspects of Lower Godavari River and Delta Sediments, India: ABSTRACT

To study the progressive changes along a river and to delineate sedimentary environments based on variations in the litho- and chemo-facies, 400 recent sediments from the fluvio-marine environment of the Godavari were collected in the pre- and post-flood seasons. The present river morphology is a manifestation of the bed load material. Higher silt-clay ratios increase the degree of sinuosity and decrease the width/depth ratios of the channels. Decrease in the sinuosity of the river course in the last one hundred years is probably a result of the coarsening in the bed load. Mean size decreases and coefficient of sorting increases progressively along the river course; skewness changes from positive to negative while kurtosis remains constant. These changes are probably attributable to the decrease in the energy levels downstream. Heavy mineral percentages are directly proportional to the mean size of the sediments. Heavy minerals indicate a predominantly igneous (acidic) and high-grade metamorphic (khondalite, calc-granulite, and amphibolite) provenance. Few authigenic and rounded zircons are considered secondary. Downstream increase of pyroboles and sillimanite, and decrease of opaques and garnets, is apparently due to sorting based on shape and density. Delineation of sedimentary environments based on conventional size measures has been partially successful. Similarity in the backwater and marine shoal sediments north of the river confluence indicates that the former was a part of the open sea. Phosphate, uranium, and iron concentrations were determined in the clay fractions. Phosphate and iron are highest in the marshes. Iron concentration decreases in the backwater and is least in the river channels. Preliminary data show higher uranium content in the upper river. X-ray analyses show illite, chlorite, and Na-montmorillonite increasing and Ca-Na montmorillonite and kaolinite decreasing from the fluvial to the marine environment. Na-montmorillonite is more predominant in the swamps and illite in the backwater. The hydrographic data collected are being processed to understand the physico-chemical conditions of deposition. End_of_Article - Last_Page 354------------

Interpretation of Sieve Analyses of Agricultural Limestones and Suggested Particle Size Specifications1

SynopsisConsiderable variation in fineness occurs among agricultural limestones from different geographical regions but most are of the ground and meal grades. Log normal plots of sieve opening diameters against cumulative percents passing, and the quartiles, median, and sorting coefficient are useful in studying particle size distributions. Specifications requiring that 50% shall pass a selected median sieve, and that 95% pass a coarser sieve, are suggested.

Maximum size, median diameter, and sorting of tephra

The many variables involved in the production, ejection, transportation, and deposition of pyroclastic fragments (tephra) with wide ranges in size, density, and shape are complex, but amenable to sedimentary statistical analysis. The parameters discussed in this report are the variations—with respect to distance—of maximum size, Wentworth grade sizes, median diameters, and sorting coefficients. Plots of these data give qualitative information on ancient wind direction and strength and on the strength of volcanic eruptions. Maximum sizes of fragments ejected from a volcano decrease as the distance from the source increases. Log-log plots of maximum size versus distance for tephra from eruptions at Crater Lake, Oregon, and Mount Asama, Japan, indicate that the tephra deposited in the northeast direction from Crater Lake was from the more powerful eruption. Fragment sizes decrease with distance from Crater Lake and Mount Asama at similar rates, which suggests that wind velocities may have been similar during their deposition. Maximum size measurements of pumice fragments from a small tephra sheet near Medicine Lake in northern California demonstrate that the wind blew northeastward during the eruption of Little Glass Mountain. Contour maps of Wentworth grade sizes of the Crater Lake pumice fall and a contour map of median diameters from the same data show three size lobes instead of the two shown by the isopach map. The differences between the contour configuration of successive gradesize maps, which result from differing distributions of fragments, are interpreted as being caused by differing wind strengths and directions at various elevations to which the fragments were ejected. Median diameter values for 114 tephra samples suggest that the minimum limit for pyroclastic comminution approaches a value near 2 μ. Log-log plots of median diameter versus distance show a complex mathematical relationship between these two parameters. The sorting coefficient of tephra generally decreases with increasing distance from source, and, as with median diameter, the mathematical variation of sorting coefficients with distance is complex. It is of interest that the mode of sorting coefficients for the 114 samples on which data are available is between 1.2ϕ and 1.4ϕ, even though median diameters range from −4.74ϕ to 6.38ϕ for distances as great as 780 km.

The Grain Size Distribution Measurement and its Bearings on Engineering Geology

From the geological survey and results obtained by the grain size analyses of the sediments of the Pleistocene system distributed between Hirao and Ishiyama, the writer has drawn the following conclusions on a part of the uppermost Kobiwako group.1) The Pleistocene system in this area is divided into two formations, the Kokubu (upper) formation and the Yakino (lower) formation.2) On the triangle diagram (pebble + sand, clay and silt), the sedimentary materials of the Pleistocene system of this area are classified into six groups in the Kokubu formation and five groups in the Yakino formation. The distribution mode of grain size is given as the bimodal distribution which consists of the traction and suspension load.3) In relation to the coefficient of sorting (So) and the medium grain size (Md), the sedimentary material of the Pleistocene system of this area is classified into six types (II, III, V, VI, VIII and IX) in the Kokubu formation and five types (II, III, VI, VIII and IX) in the Yakino formation. The writer proposes to call their grain size rank the “So-Md Rank”.4) By plotting the medium grain size (Md) on Hjulstrom's diagram, it was clarified that Md is proportional to the settling velocity (Sv) and is in inverse proportion to the critical velocity (Cv), and also the coefficient curve of sorting is recognized as the interrelation curve between the critical and settling velocity curves.5) The transition of the grain size type, depositional movement and index number of sedimentary facies of the Kokubu formation is conspicuous in comparison with the Yakino formation. It may be deduced, therefore, that the former is the disturbed zone nearer to the lake beach than the latter in the sedimentary environment.6) The difference of the background between the two formations may be suggested by the difference in their sedimentary materials.7) From the relation of “N value” and index number of plasticity, the upholding strength of each grain size type is divided into A, B and C in grade. The relation between each grade is shown as A>B≥C.8) The rate of increase of the upholding strength of each grain size type is in inverse proportion, thus |K-r| = e.K : rate of contained water, r : index number of plasticity.9) The strata conspicuous in the transition of the sedimentary environment may be conspicuous in the transition of the grain size type and upholding strength.

Effect of Climate and Source Area Location on Browns Park Formation Petrology: ABSTRACT

The Browns Park Formation of Miocene age consists dominantly of cross-bedded feldspathic sandstones and was deposited by a series of northward flowing rivers that headed in the vicinity of the San Juan Mountains. The sandstones were transported 150 to 250 miles to northwestern Colorado and south-central Wyoming. Abundant plutonic and volcanic rock material show that the sandstones are largerly first cycle sediments. The quartz, feldspar, volcanic rock fragments, and heavy minerals all are considerably rounded; some are very well rounded. The freshness of much of the feldspar demonstrates that corrosion at the source is not responsible for the rounding, but the distance of fluviatile transport is too short to explain the degree of rounding. The quartz grains are commonly frosted and pitted, considered to be due to eolian action. The rounding of the sand grains apparently took place during intermittent periods of eolian activity. Fluviatile transport associated with eolian activity suggests a semi-arid climate. Volcanic centers in northern Utah and southern Idaho have been suggested as a source of the volcanic material which occurs abundantly in the Browns Park Formation. Grain size determinations of quartz, feldspar and volcanic rock fragments showed an increase in size of all components toward the south and not toward the suggested western area. The mean grain size, sorting coefficient, and other grain-size parameters are similar in the quartz, feldspar and volcanic material. This relationship suggests that volcanic material was carried an appreciable distance with the other components in the sandstone. The grain-size characteristics of the volcanic-rich Browns Park sandstones indicate that most of this material was derived from volcanic centers in the San Juan region. End_of_Article - Last_Page 353------------

On Sorting, Sorting Coefficients, and the Lognormality of the Grain-Size Distribution of Sandstones

The coefficient of sorting in sedimentary petrography is commonly considered to be the statistical measure introduced by Trask. Several investigators have objected to the use of the Trask coefficient on theoretical grounds. Others have continued to uphold its usefulness. Two new sorting coefficients have been introduced within recent years (Inman's and Folk and Ward's sorting measures), based on the geometry of the normal curve. On theoretical grounds these measures should more adequately describe the sorting characteristics of sediments than does the coefficient of Trask. However, some practical considerations argue against the use of these new sorting parameters for many types of sediments. Empirical correlations have been made in this study between the three sorting measures (Trask's, Inman's, and Folk and Ward's) and the standard deviation. The standard deviation is a moment measure which represents the most suiTable statistic for describing the sorting characteristics of sedimentary rocks. The empirical correlations permit an appraisal of the advantages and disadvantages of each sorting parameter which has not been possible in the past. Correlation diagrams show that both the Trask coefficient and the Inman sorting measure approximate the standard deviation and that a high correlation exists between the standard deviation and the sorting measure of Folk and Ward. The Inman measure is more satisfactory for describing the sorting of moderate to poorly sorted sandstones. The Trask coefficient is more satisfactory for describing very well to well-sorted sandstones. The Folk and Ward sorting measure appears to be satisfactory for the entire range of sorting characteristics. A new genetic classification of sorting based on the standard deviation and on environmental significance is recommended. The standard deviation ranges for sands from different environments are tabulated. Three figures in this paper demonstrate how the standard deviation of the sediment distribution compares with the sorting coefficients of Trask, Inman, and Folk and Ward. Trask sorting values corresponding to the class intervals of the recommended standard deviation classification serve as a new sorting classification for studies where grain size is expressed in millimeters. A new genetic classification of sorting based on the standard deviation and on environmental significance is recommended. The standard deviation ranges for sands from different environments are tabulated. Three figures in this paper demonstrate how the standard deviation of the sediment distribution compares with the sorting coefficients of Trask, Inman, and Folk and Ward. Trask sorting values corresponding to the class intervals of the recommended standard deviation classification serve as a new sorting classification for studies where grain size is expressed in millimeters. To determine the extent of deviation from lognormality of the grain-size distribution of sandstones, a more sensitive method than the straight-line probability plot has been employed. A normal curve can be defined as a frequency distribution which has a skewness (third moment) of 0 and a kurtosis (fourth moment) of 3. A study of 612 ancient and modern sand samples indicates that the grain-size distribution of most sands and sandstones does not follow a lognormal function. Omitting the sign for skewness, the mean for skewness for the samples studied is 0.76 and the mean for kurtosis is 5.31. These data indicate that the grain-size distribution curve of the average sand is skewed and considerably more peaked than that of the normal curve. There is a tendency for deviation from lognormality as the sands are being deposited. River and dune sands are for the most part positively skewed, whereas beach sands are generally negatively skewed. Deviation from lognormality of the grain-size distribution of sands is an environment-sensitive parameter. The standard deviation (sorting index) of a sand is another significant environment-sensitive textural attribute. plot of deviation from lognormality as expressed by the skewness (third moment) against the sorting index (standard deviation) for medium-to fine-and very fine-grained sands serves to distinguish beach sands from river sands.

Relationships Between Porosity, Median Size, and Sorting Coefficients of Synthetic Sands

ABSTRACT The relationship between porosity, median size, and sorting coefficients has been investigated by studying synthetic sands with lognormal size distributions and various median sizes and sorting coefficients. Poorly sorted sands are considerably less porous than well sorted ones, and porosities show an inverse linear relationship to sorting coefficient except in very well sorted samples in which porosity increases more rapidly than sorting. Porosity is independent of median size in well sorted sands but appears to decrease slightly with increasing median size in poorly sorted sands. The relationship between median size and porosity probably results from the fact that larger grains have a higher sphericity and tend to pack more closely together than smaller, more irregularly shaped grai s.

Bottom Sediments of Georges Bank

ABSTRACT A survey of Georges Bank bottom sediments was undertaken to provide basic data for use in studying the relationships between substrate composition and the occurrence of benthic animals, especially those which are common foods of fishes. Particle side composition is the principal sediment character that was studied. Six statistical measures of particle size composition are given in order to designate the main features of the size-frequency distribution of each sample. These measures are: median diameter, mean diameter, coefficient of sorting, kurtosis, and two measures of skewness. In addition to these parameters, organic content, shell content, color, and textural classifications are included. In the presentation and discussion of the data, special emphasis is given to the geographic distribution of the various sediment constituents and particle size composition.

Composition, Grain Size, Roundness, and Sphericity of the Potsdam Sandstone (Cambrian) in Northeastern New York

ABSTRACT The Potsdam Sandstone of Late Cambrian age crops out along the north, east, and southeast borders of the Adirondack Mountains in northeastern New York State. It has generally been described as an orthoquartzite. In the Mooers area, however, the Potsdam is mainly a subarkose or arkose. Detailed analysis of 10 thin sections of the Potsdam Sandstone from the Mooers Quadrangle provide data for grain-count composition, median grain size, cumulative size curves for individiaul samples, mean grain size, coefficient of sorting, roundness, and sphericity. The examination of 25 additional thin sections provided data for a lithofacies map. In the Mooers area, the Potsdam can be distinguished from the sandstone in the overlying Theresa Dolomite, which, unlike the Potsdam, contains no zircon, very little feldspar, and very well rounded quartz grains. Mean grain roundness in the Potsdam ranges from 0.4 to 0.5; sphericity ranges from 0.73 to 0.79. The relation of roundness to sphericity is similar to that reported in other published studies. The median size decreases and sphericity increases to the north, away from outcropping Precambrian rocks. Sorting is best and median grain size smallest where the beds dip least, suggesting that the dip is probably primary. Sedimentary analysis by thin-section techniques gives abundant, fairly reliable quantitative data for sedimentary studies.

Rochas Clásticas do Planalto de Poços de Caldas

Rochas Clásticas do Planalto de Poços de Caldas

Formation of the Crystal-Rich Glowing Avalanche Deposits of St. Vincent, B.W.I.

Andesitic glowing avalanches discharged from the Soufriere of St. Vincent on May 7, 1902, deposited ash which is noted for its fine-grained texture and richness in crystals. The largest avalanche deposit of this eruption contains several per cent of blocks and bombs and 15-30 per cent of lapilli. The median diameter in a representative sample is 0.6 mm., and the sorting coefficient is 2.9. Crystals form 45 per cent of the bombs and have been concentrated to form almost 58 per cent of all juvenile material in the deposit and 73 per cent of the juvenile ash finer than 2 mm. The glowing avalanches were discharged from the outer part of a vertical ash column which carried a large volume of ash to considerable elevations. When the column became denser than the surrounding atmosphere, it discharged clouds of pyroclastic material laterally. The clouds quickly became stratified into a lower, denser fraction (the glowing avalanches) containing the coarse ejecta and bulk of the crystals, and an upper part lighter and richer in gas and fine particles of vitric ash. A third or more of the material discharged was dispersed in the light, gas-rich clouds which accompanied the avalanches during their descent. Glowing avalanches discharged by prehistoric eruptions which reached a climax 4,000 years ago deposited materials essentially similar to those of 1902. The prehistoric avalanche deposits, together with mudflows and stream-laid materials, filled valleys on the western side of the Soufrière and formed a large fan at its eastern foot. The St. Vincent glowing avalanche deposits are chemically, mineralogically, and textura Jly rather similar to a number of pumice- and scoria-flow deposits. Crystals have been concentrated in the ash fraction of pumice-flow deposits of Crater Lake and Asama beyond their proportion of the magma, probably by the same mechanism as they were concentrated on St. Vincent. A scarcity of bombs in the St. Vincent deposits is apparently the only major difference between these and the scoria- and pumice-flow deposits of other volcanoes.

Textural Differences Between Two Types of Shoestring Sands: ABSTRACT

Exploitation of oil and gas accumulations in shoestring can be aided materially by determining, with samples from even a single well, whether a sand stringer is an offshore bar deposit with a linear shape and lying parallel with the depositional trend, or whether it is a river deposit cutting across the depositional trend and having a sinuous shape. The present research has disclosed textural criteria applicable to well samples which serve to differentiate these two types of shoestring sands. Samples taken from rivers and from beaches along the Texas Gulf Coast indicate clear textural differences between the two environments. Compared with river sands, beach sands show an extremely restricted range of mean sizes and sorting coefficients. Furthermore, river sands with sorting coefficients equal to those of beach sands are invariably coarser than beach sands, whereas river sands of the same mean size as beach sands are more poorly sorted. Consequently, plots of mean size versus sorting yield a clear distinction between the two types of sediment. The foregoing information has been obtained by sieve analyses of unconsolidated sediments. Mean sizes and sorting coefficients of sandstones, however, can be approximated readily by grain counts in thin sections. In 15 minutes, or less, sufficient grains can be counted in section to enable the geologist to differentiate the typical beach and river sands studied in the present work. End_of_Article - Last_Page 2516------------

Mechanical analysis of the sandstones of the Shinjo group. (III)

Statistical studies of the clastic sediments of the Shinjo group have been carried out under the same mechanical treatment as in the previous work. In this paper the Masugata and Kawaguchi areas are used as the test areas for investigating the characteristics and the variations of the sediments. Four types are recognized as the result of the mechanical analysis (median diameter, coefficient of sorting, standard deviation, skewness, and kurtosis). The types Ma and Mb in the Masugata area are practically correlated with the Mitsumori-Sakegawa-Yamuke and Shimizu-Izumikawa formations, and the types Ka and Kb in the Kawaguchi area with the Sakegawa-Yamuke and Shimizu-Izumikawa formations respectively. At least it is possible to be recognized that the marker bed K4 between the Yamuke and the Shimizu is found to be the clear indicator in the vertical differentiation also in these areas as shown in the previous discussion.