Inclusive Graphic Standard Deviation Research Articles

Analysis of size, shape and textural maturity of sands from the Kaligandaki River

The Gandaki River System is one of the major river basin of the Himalaya originating from China and flows through Nepal and eventually mixes with the Ganga River in India. The study aims at analyzing the textural properties (size and shape) and maturity of the Kaligandaki River sands, and their downstream variation. Sand samples were collected along the river from the Tethys Himalayan region up to the Indo-Gangetic Plain of Nepal. The sands are classified as slightly muddy sand, in which mean and median sizes and sorting increase with respect to the distance downstream from the provenance. The results indicate that coarsely skewed and platy to mesokurtic sands become nearly symmetrical to finely skewed and leptokurtic suggesting increase in fine-grained sands and enhancement of sorting downstream. The percent of fines (mud) ranges from 0 to 5% and shows no distinct downstream variation trend. Mean roundness of quartz is generally sub-angular (2 to 3 p), and downstream variation does not reflect change in roundness category. However, there occurs slight diminish of roundness with distance downstream. Inclusive graphic standard deviation (Cj) varies from 0.30 to 1.38j. After 100 km downstream, Gj decreases reflecting improvement of sorting. Sediments are immature to mature, and are sub-mature in upstream and midstream segments except for few sites where they are immature not due to flux, but probably due to local contribution of fines. Due to increased downstream distance, sediments tend to be more mature owing to enhancement of sorting

Sedimentological study of Bima sandstone in Dumne and Environs, Yola Sub-basin, Upper Benue Trough, Northeastern Nigeria.

Field mapping was carried out on Bima sandstone from Dumne and its environs with the aim to understand the geology and determine the paleoenvironment of deposition. The integrated (outcrop study with granulometric and pebble morphometric) studies were used to achieve this aim. Based on outcrop studies, nine (9) lithofacies were identified from the proximal alluvial fan facies to the mid-fan braided river: massive, matrix-supported, gravel-dominated facies (Gmm); matrix-supported gravel (Gmg); clast-supported gravel stratified (Gh); gravel stratified trough cross-bedded sandstone (Gt); trough cross-bedded sandstone (St); planar cross-bedded sandstone (Sp); ripple cross-laminated sandstone (Sr); massive sandstone (Sm) and silt and mud (Fsm). The outcrop sampled materials were subjected to granulometric and morphometric analyses. The result of the granulometric shows that the Bima sandstones of the study area have an average graphic mean (Mz) of 0.82 (coarse grains), an inclusive graphic standard deviation (δi) of 1.33 (poorly sorted), a graphic kurtosis (K) of 1.11 (leptokurtic), and an inclusive graphic skewness (Ski) of 0.17 (positive skewed). The result of the pebble morphometrics shows that the grains have an average elongation ratio (ER) of 0.80, coefficient of flatness (FI) of 60.6%, oblate–prolate index (OPI) of 0.35, maximum projection sphericity index (MPSI) of 0.77 and roundness (ρ) of 0.43. The roundness versus elongation ratio plot indicates a fluvial to transitional environment. Several bivariate and ternary plots that include the granulometric and pebble morphometric data suggest a river environment for the Bima sandstone in the studied area.

Environments of upper miocene sediments in the Hanoi depression interpreted from grain-size parameters

The grain-size analysis is carried out for 49 samples of Upper Miocene sediments taken from three boreholes in the Hanoi depression. The statistic parameters of the grain size distributions such as percentiles, median, graphic mean, sorting or inclusive graphic standard deviation, inclusive graphic skewness, and graphic kurtosis are used to decipher the depositional environments and transportation mechanisms of sediments. Bivariate plotting of these parameters, the discriminant functions with four basic parameters of graphics mean, sorting, inclusive graphic skewness and graphic kurtosis, and the CM pattern with the one percentile (C) and median (M) diameters are applied for this determination. The plots of graphics mean versus sorting suggest 14% of samples being the sand sheet, 46% related to rivers and 40% of the estuarine environment. The sorting - inclusive graphic skewness plot shows a river-related environment for all samples. Linear discriminant functions show the sandstone of upper Miocene in Hanoi depression are deltaic sediments formed in unstably transporting and depositional environment, impacted by turbidity current in the coastal river-mouth. The CM pattern shows sediment transportation for most of the samples in three modes: rolling, suspension and rolling, and uniform suspension. The environmental dynamics are relatively complex and change over time.

Granulometric and pebble morphometric applications to Benin Flank sediments in western Anambra Basin, Nigeria: proxies for paleoenvironmental reconstruction.

Integrated granulometric and pebble morphometric study of Late Cretaceous rocks of the Benin Flank, Nigeria, were used to delineate depositional process and environment of the rocks in the study area. Granulometric analysis reveals that the sandstones of the Lokoja Bassange Formation have an average graphic mean (Mz) of 0.59Φ (coarse grains), inclusive graphic standard deviation (δi) of 1.36Φ (poorly sorted), graphic kurtosis (Ka) of 1.12Φ (leptokurtic), and inclusive graphic skewness (Ski) of - 0.14Φ (stongly coarse skewed). The sandstones for the Mamu Formation have an average Mz of 1.42Φ (medium grains), inclusive graphic standard deviation (δi) of 0.74Φ (moderately sorted), graphic kurtosis (Ka) of 1.43Φ (leptokurtic), and inclusive graphic skewness (Ski) of 0.02Φ (nearly symetrical). The sandstones for the Ajali Formation have an average Mz of 1.23Φ (medium grains), inclusive graphic standard deviation (δi) of 1.21Φ (poorly sorted), graphic kurtosis (Ka) of 1.46Φ (leptokurtic), and inclusive graphic skewness (Ski) of - 0.17Φ (nearly symetrical). Pebble morphometric analysis of the larger grains reveals that the mean values of elongation ratio (ER) = 0.69, coefficient of flatness (FI) = 54.90%, oblate-prolate index (OPI) = 3.34, the maximum projection sphericity index (MPSI) = 0.75, form = 0.67, and roundness (ρ) = 36.28% for the Lokoja Bassange Formation; ER = 0.76, FI = 37.07%, OPI = -3.20, the MPSI = 0.53, form = 0.38, and ρ = 52.93% for the Mamu Formation; and ER = 0.72, FI = 47.44%, OPI = 1.12, the MPSI = 0.67, form = 0.54 and ρ = 42.68% for the Ajali Formation. The integration of the various granulometric and pebble morphometric data, different bivariate and ternary plots indicate fluvial environment for the Lokoja Bassange Formation, dominantly shallow marine environment for the Mamu Formation and fluvial - shallow marine environment for the Ajali Formation. This study shows that the Benin Flank, western Anambra Basin has a depositional setting radiating between fluvial and shallow marine environments.

Provenance Analysis of Sediments in ILU-TITUN and Environs, Eastern Dahomey Basin, Ondo State, Nigeria

Twenty eight sediment samples were obtained from road cuts and stream cuts in Ilu Titun area of Ondo State, Nigeria and were subjected to Grain Size Distribution (GSD) analysis, from which statistical parameters were calculated and used to determine the environment of deposition of the sediments. Six representative samples were selected for petrographic studies to determine the heavy mineral content of the sediments with a view to establishing the sediments source of Ilu Titun and environs which mark the eastern margin of the Dahomey basin. The Graphic Mean (Mz) ranges from 0.700F to 1.667&Phi while the Inclusive Graphic Standard Deviation (&sigma i ) range from 0.960 to 1.319. The Inclusive Graphic Skewness ( SK I ) of the samples ranges from -0.665 to 0.803 while Kurtosis range from 1.652 to 3.309. The bivariate plot of mean size against the Inclusive graphic standard deviation show that the sediments were deposited by river and beach processes. The plot of skewness against the Inclusive graphic standard deviation confirmed that the sediments were deposited by river processes. The results of the petrographic studies show that Slides EK 01 and EK 08 have Kyanite and Staurolite. Slides EK 13 and EK 24 have Staurolite, Tourmaline and Garnet. Slides EK 26 and 28 have Tourmaline and Zircon present in them. Bivariate plots using the statistical parameters show that the sediments were deposited by fluvial processes. The results from the petrographic studies indicate that the sediments were sourced from metamorphic rocks and pegmatites.

MINERALOGY AND RADIOACTIVITY STUDIES OF WADI YOIDER STREAM SEDIMENTS, SOUTH EASTERN DESERT, EGYPT

Wadi Yoider area is located in the South Eastern Desert of Egypt, covering an area of about 150km2. It is covered by basement rocks dissected by Wadi Yoider as a main wadi with several tributaries. The rock types cropping out at Wadi Yoider area comprise, from the oldest to youngest, metavolcanics, younger gabbros, alkali feldspar granites, muscovite granites, biotite granites, monzogranites, and wadi deposits (quaternary sediments) filling the streams of the studied area. The results of the sedimentological statistical parameters are graphic mean (Mz) indicate that, they range from 0.04 to 1.8 with average 0.85, inclusive graphic standard deviation (σI) ranging from 0.88 to 1.8 with an average 1.2, inclusive graphic skewness (SkI) ranging from 0.03 to 0.33 with an average 0.2, and inclusive graphic kurtosis (Kg) ranging from 0.68 to 2.05 with an average 1.4. These samples are characterized by fine skewed, neer skewed, coarse skewed, platykurtic and mesokurtic. All these features indicate of a turrstile. Gravity and magnetic separation techniques in addition to microscopic examination for the studied stream sediment samples were applied to identify the heavy minerals in these sediments. These minerals are represented by magnetite, ilmenite, hematite, rutile, leucoxene, garnet, titanite, zircon, and samarskite. The average concentrations of U and Th in the stream sediments of Wadi Yoider are 20.2ppm and 42.2ppm, which are higher than the clarke values for earth crust

CONTRIBUTION TO THE MIERALOGY AND RADIOACTIVITY OF STREAM SEDIMENTS OF WADI RAS BAROUD AREA, NORTH EASTERN DESERT, EGYPT

Wadi Ras Baroud area is located in the North Eastern Desert of Egypt, covering an area of about 170km2. It is covered bybasement rocks and dissected by several wadies. The rock assemblages cropping out at Wadi Ras Baroud area comprise, quartzdiorites, granodiorites, syenogranites, dykes and Quaternary sediments filling the streams of the studied area.The grain size analysis and their distribution is a fundamental descriptive measure for clastic sediments. The results of thestatistical parameters are a graphic mean (Mz) ranging from 0.4 to2, inclusive graphic standard deviation (I) ranging from1.2 to 1.9, inclusive graphic skewness (SkI) ranging from -0.3 to 0.22, and inclusive graphic kurtosis (Kg) ranging from 0.7 to1.1. These parameters clear that they are coarse to medium sand, poorly sorted, near to coarse skewed samples, and platykurticand mesokurtic, so these sediments are represented by the turbidity currents environments.The identified minerals in the heavy fractures are represented by magnetite, ilmenite, hematite, garnet, rutile, titanite, zircon,thorite, ferogusnite, and columbite. The radiometric study of the stream sediments of Wadi Ras Baroud indicates that theaverage concentrations of U and Th are 10.38ppm and 25.5ppm respectively

Size Analysis of the Late Pliocene-Early Pleistocene Upper Siwalik Sediments, Northwestern Himalaya, India

Size analysis of the Late Pliocene-Early Pleistocene Upper Siwalik sediments comprising the Pinjor Formation in the type area and adjoining regions reveals that the sediments are bimodal to polymodal in nature, medium to fine grained and are moderately sorted. The inclusive graphic standard deviation and moment standard deviation values suggest the deposition of sediments in shallow to moderately deep fluvial agitated water. The log probability plots reveal that saltation mode is the dominant mode of transportation of detritus. The sediments are continental in character and are derived from crystalline, metamorphic and sedimentary rocks of the Himalaya exposed to the North of the type area Pinjor.

Geographic mosaic of mutually exclusive dominance of obligate commensals in symbiotic communities associated with a burrowing echiuran worm

Species richness and community composition of symbionts associated with the burrowing echiuran worm, Ochetostoma erythrogrammon Leuckart & Ruppell, 1828, were quantitatively surveyed on subtropical intertidal flats in the Ryukyu Archipelago, Japan. Overall, we recorded seven species of burrow associates, including at least six obligate commensals. According to symbiont community composition, the study sites were largely divided into two groups; one was characterized by the dominance of a snapping shrimp, Alpheus barbatus Coutiere, 1897, and the other by the dominance of a scale worm, Lepidonotus sp. Furthermore, a granulometric analysis showed that the sediment characteristics differed significantly between shrimp- and scale worm-dominant sites in terms of median diameter and inclusive graphic standard deviation. These results suggest that these symbionts have different habitat requirements, resulting in the mutually exclusive dominance pattern. Our findings indicate that habitat heterogeneity is important to the evaluation and conservation of the symbiotic diversity in intertidal flats.

Nearshore Macrobenthic Communities off Two Nuclear Power Plants in Northern Taiwan

The nearshore macrobenthic communities outside the Nuclear Power Plants Ⅰ and Ⅱ were monitored on a seasonal basis from winter, 2000 to summer, 2004. The animal and sediment were sampled by scuba diving. The macrobenthic assemblages, sediment characteristics and total organic content were analyzed. The macrobenthos assemblages in terms of species richness, density and biomass was determined. The mean grain size and sorting (i.e. inclusive graphic standard deviation) of sediment were also determined. The small-sized annelids and crustaceans were the dominant macrobenthos. A total of 96 species of macrobenthos was found in the sediment near the Nuclear Power Plant Ⅰ. The sediment was composed mainly of moderately sorted coarse sand, with silt-clay content less than 2%. The total organic Content ranged from less than 1% to 7%. A total of 86 species of macrobenthos was found in the sediment near the Nuclear Power Plant Ⅱ. The sediment composed mainly of moderately well sorted medium sand, with silt-clay content equal or less than 4%. The total organic content ranged from 1% to 4%. The short distance between two power plants resulted in about 50% of species shared by both plants. Statistical analyses showed that the macrobenthic communities in the relative open system outside the Power Plant Ⅰ were more affected by season than by the sediment characteristics. The relative protected environment outside the Power Plant Ⅱ resulted in higher habitat diversity. The sediment characters strongly influenced to the macrobenthic communities. The synoptic comparisons between two power plants showed that in spite the differences in the microhabitat, the nearshore macrobenthic communities in the Northeast Taiwan were mainly affected by the sediment characters. Seasonal variation was the secondary factor. Results of this study found that the influence of thermal effluent from the power plant to the nearshore macrobenthic community structures was rather localized. Nearshore macrobenthic communities appeared to have reached a stable condition with the constant environmental disturbances from the power plants.

Small-scale non-linear geostatistical analysis of Liocarcinus depurator (Crustacea: Brachyura) abundance and size structure in a western Mediterranean population

The small-scale spatial distribution of density and biomass of the crab Liocarcinus depu- rator off the Ebro delta was analysed using universal kriging (non-linear geostatistics), considering depth as an external trend. In order to understand the spatial distribution of crab size, a third variable was created from the residuals of the non-linear regression between biomass and density. Variogram analysis of crab density and residuals of the biomass/density relationship presented a quadratic rela- tionship with depth, while biomass showed a linear relationship with depth. All experimental vario- grams were fitted to spherical models. The patch size (range) found was 10.64 km for density, 14.53 km for biomass and 20.49 km for the residual variables. The spatial distribution of 8 sediment variables (temperature, redox potential at 1 and 6 cm depth (R1 and R6), carbonate content (CO3), median grain size (ϕ), sediment sorting (IGSD: inclusive graphic standard deviation) and organic matter content (OM)) was studied. The maps obtained were compared with those calculated for the biological variables of L. depurator using Mantel and partial Mantel tests. Distribution characteristics of this species were significantly affected by most sediment variables considered, particularly by tem- perature, organic matter content and redox potential, although overall the correlation level was low, coinciding with the generalist ecological role and opportunistic behaviour of the species. Density and biomass, as well as residuals, presented a negative correlation with the sorting coefficient (IGSD) and with carbonates. In relation to IGSD, high densities of L. depurator were found in homogeneous sed- iments. Residuals (size structure of the population) were significantly correlated with grain size (ϕ), with larger individuals occurring in finer sediments, while juveniles were preferably found in areas with very fine sand sediments. Both density and biomass presented significant positive correlations with the redox potential, indicating that the species favoured well-oxygenated sediments with a low organic content.

Análise dimensional de sedimentos fluviais: formação de Alvarães e depósitos de terraços da bacia do rio Lima (NW de Portugal)

Trata-se dum estudo das distribuições dimensionais de sedimentos fluviais Plio-Quaternários do NW de Portugal pertencendo: à Formação de Alvarâes (enchimento da «bacia de Alvarães»), aos depósitos dos terraços do rio Lima e depósitos dos terraços dos afluentes deste rio. As distribuições dimensionais foramobtidas por: crivação dos sedimentos>62um num agitador mecânico de tipo RO-TAP, segundo uma escala dimensional com intervalos iguais a V2, e pipetagem das suspensões<62um com a pipeta de Andreasen. A interpretação é baseada nos parâmetros estatísticos média, desvio padrão, assimetria e curtose, calculados segundo as fórmulas de FOLK-WARD (1957), e diagramas CM (PASSEGA 1957).

Distribuição de freqüência de tamanho da fração areia e compacidade relativa de solos desenvolvidos de sedimentos do grupo geológico barreiras

A condição de adensamento do solo tem importância para orientar o manejo de uma área. Em solos derivados de sedimentos recentes, a propensão ao adensamento pode estar relacionada com as características herdadas das condições de sedimentação. Em uma toposseqüência de solos desenvolvidos de sedimentos arenosos do grupo geológico Barreiras, no município de Caravelas (BA), selecionaram-se oito perfis de solos, sendo cinco deles sob Eucalyptus, abrangendo Gley Pouco Húmico, Podzol Hidromórfico, Podzólico Amarelo e Plintossolo. Foi determinada a densidade aparente, a qual foi posicionada entre a densidade aparente mínima e a máxima, definindo-se, assim, a compacidade relativa para cada um dos 41 horizontes. A areia foi fracionada em 21 classes de tamanho, mediante peneiramento, determinando-se o diâmetro médio, o desvio-padrão gráfico inclusivo, a assimetria gráfica inclusiva e a curtose gráfica. Observou-se que o maior teor de areia fina e mal selecionada facilitou o arranjo mais compacto das partículas, provocando aumento na compacidade relativa nos horizontes de maior resistência à penetração.

Abstract: Nearshore Morphology and Sediment Characteristics Along Ward Island, Corpus Christi, Texas

ABSTRACT Texas A&M University-Corpus Christi is sponsoring a study on the feasibility of a recreational beach for its campus located on Ward Island. The beach would front the northern shoreline of Ward Island along Corpus Christi Bay, Corpus Christi, Texas. The functional design process provided an opportunity to investigate the nearshore morphology and sediment characteristics of this unstudied shore. Seasonal profile surveys were conducted from the spring of 1994 to the winter of 1996 and included sediment sampling along select transects. Repetitive profile surveys taken along the same transect proved average survey elevation accuracy to be better than 0.7 cm. The surveys extended the entire 2.6 km length of the northern Ward Island shoreline from the Oso Inlet to the Blind Oso Inlet. An unusually flat and wide nearshore region was identified. The shallow (1.1 m) nearshore typically extends 150-200 m offshore. The depth of closure, or active region of sediment transport, is at 1.6 m Mean Tide Level, as identified through profile surveys. The sediment in the nearshore is moderately sorted, inclusive graphic standard deviation of 0.02 mm, fine sand with a median grain size diameter of 0.14 mm. The survey defined a well-developed longshore bar system that was previously observed visually during periods of low tide and in aerial photographs. This system consists of four to seven sandbars that slowly migrated offshore during the study period, independent of season. Inspection of aerial photographs taken from 1934 to 1996 indicate that the number and linearity of longshore bars has decreased. In addition, the bars west of the Blind Oso Inlet appear to be superimposed on a raised subsurface feature. This plateau was also identified at Poenisch Park, located west of Ward Island, indicating that the sandy nearshore region is a veneer over a firm relic shelf. This study hypothesizes that the decrease in number and linearity of the longshore bar system is related to a decrease in sand resources. Thus, natural accretion of a beach along Ward Island is unlikely. Therefore sandy-fill material along with coastal structures will be necessary to provide a stable beach in this region.

A comparison of surface sampling methods for coarse fluvial sediments

In order to characterize variability associated with sampling coarse fluvial sediment, surface grain‐size distributions were characterized at eight sample sites within gravel‐ to boulder‐bed channels. Four methods were used: (1) a random walk, (2) a sampling grid spaced at an interval equal to the intermediate diameter of the largest clast in the sampling area, (3) a sampling grid spaced at one half the interval of method 2, and (4) a randomly chosen subsection within which a patch count of most clasts at least partially exposed at the surface was conducted. At each site, six replicates of each method were performed, with each replicate consisting of 100 clasts. Sampling was performed by a single operator at six of the sites and by multiple operators at two of the same sites and at two additional sites. The research objectives were to characterize variability among replicates of a method, among methods, and among operators. Sample sites were divided into relatively well sorted (inclusive graphic standard deviation <1.4) and poorly sorted (≥1.5). The first three methods produce statistically indistinguishable values of D50 and D84 for both well‐sorted and poorly sorted sites when performed by a single operator. Multiple operators may produce statistically different population measures (D50, D84, sample distributions, and variance) using any of the four methods at either type of site. Because of operator‐induced variability, we caution against direct comparisons of grain‐size distributions between channels or within a single channel through time if more than one operator performs the sampling.

Comparative studyes of moment, graphic and phi measures on the sands of the East Coast beaches, India

A comparative study of moment, phi and graphic parameters, at 1 4-φ class interval, has been undertaken on 120 representative samples, selected out of 2000 samples from four beaches along the East Coast of India. The results show very good correlations among graphic, phi and moment means (correlation coefficient = 0.99), and among inclusive graphic standard deviation, phi standard and moment standard deviations (correlation coefficient = 0.90). Thus, they may be computed by any of these methods without any significant differences. The linear correlation between inclusive graphic skewness and graphic skewness is found to be good (coefficient of correlation = 0.99) whereas the moment and graphic skewness (of Folk and Ward and Inman) show lower correlation (0.54). Coefficient of correlation between graphic and moment kurtosis is much less (0.42) and, therefore, these are not comparable.

Empirical Conversion Equations for Thin-Section and Sieve Derived Size Distribution Parameters

ABSTRACT Using size analyses of ancient sandstones, thin-section-to-sieve and sieve-to-thin-section empirical conversion equations have been derived, via linear regression analysis, for several graphical size distribution statistics: median, graphic mean, inclusive graphic standard deviation, graphic standard deviation, inclusive graphic skewness, graphic skewness, and graphic kurtosis. The correlation coefficients for each of these are respectively .958, .944, .705, .786, .567, .234, and .316. Conversions of high accuracy are possible only for the median and graphic mean. The thin-section-to-sieve conversion equations for these two parameters are, median: Y(sieve)= .121 4 + 1.030 · X(thin-section) mean: Y(sieve) = .227 + .973 · X(thin-section) Thin-section-to-sieve empirical conversion equations, of generally high accuracy, have also been derived for the following cumulative percentiles: 2, 5, 9, 16, 25, 36, 50, 64, 75, 84, 91, 95, and 98. These may be used in the conversion of whole distributions.

The sliding bed facies in esker sands and gravels: a criterion for full‐pipe (tunnel) flow?

ABSTRACTThe Guelph esker (Ontario, Canada) consists of a sinuous, steep‐sided and segmented ridge which comprises poorly sorted, matrix‐supported sands and gravels. These sands and gravels were probably deposited during the sliding bed stage which has been observed by others in closed‐conduit hydraulic experiments. The poor sorting probably resulted from a high concentration of bed‐material load in the lower part of a subglacial tunnel, sorting being restricted to that produced by particle collisions. Inclusive graphic standard deviation is characteristically large for the sands and gravels, indicating that virtually all sizes available were in transport. The overall grain size distribution shows a characteristic undulatory shape on arithmetic probability paper, mostly because of selective removal of pebble gravel and granule sizes. This poorly sorted fades is believed to be diagnostic of transport in a subglacial tunnel flowing full of water, and may be used to identify subglacial conditions in other eskers. Deltaic sands and gravels occur downcurrent of the esker and contain a greater diversity of structures; climbing‐ripple cross‐laminae, parallel laminae and massive structure, deposited in large‐scale foresees at the end of a subglacial tunnel. These deltaic sands and gravels grade distally into outwash sands and gravels.

Polymodal Composition of Beach Sands from the East Coast of India

ABSTRACT The size frequency distribution of subaerial sands of an actively eroding beach situated in the east coast of India is polymodal in nature. The degree of polymodality varies over different parts of the foreshore. The graphic mean size of sediments lies within 1.0 and 4.0 phi values. Analysis shows that the regressions of inclusive graphic standard deviation and inclusive graphic skewness on graphic mean size, determined separately for the different size groups, viz medium sand (1.0 phi to 2.0 phi), fine sand (2.0 phi to 3.0 phi) and very fine sand (3.0 phi to 4.0 phi), are different. Medium-grained sands are positively skewed; sorting improves with increasing size. By contrast, very fine sands are mostly negatively skewed; sorting improves with decreasing size. For the fine sand group the mean size and sorting is moderately correlated; however, the attitude of the regression lines in this and in the very fine sand group is somewhat similar. Sands of all the size groups when considered together exhibit an improvement in sorting and a change of skewness from positive to negative values with decreasing size. The distribution represents mixing of population and the polymodality depends on it. The ultimate nature of these mixed sediments is related to: 1) the permeability of the beach surface, 2) the availability of a wide range of sizes of sand particles, and 3) the original character of incoming sediments. Supply of a wide range of particle sizes in the study area has mostly resulted from extensive erosion of coastal dunes and marine terraces bordering the coastline. However, on an aggrading coast one may expect different results.

Integrated investigation of the mixed origin of lunar sample 72161,11

Sample 72161,11 (dark mantle at LRV-3) has a graphic mean grain size (Mz) of 3.88 o, inclusive graphic standard deviation (σI) of 1.29, and a total carbon content of 204µg C g−1 sample, and is, therefore, quite mature. However, the agglutinate content is only 30% in the 90–177µm particles, indicating an apparent departure from steady state. Analyses of C, CH4, and H2 concentrations in size fractions larger than 149µm show that the volume correlated component of these species increases with increasing grain size. In a homogeneous agglutinate population the volume correlated component is expected to be independent of grain size. The observed increase can be interpreted in terms of the mixing of a dominant local population of coarser agglutinates, with high carbon and hydrogen, with an imported population of finer agglutinates relatively poor in carbon and hydrogen. When analyses of size-fractions from the bulk sample are considered, these effects are apparently obliterated by the admixture of coarse-grained material low in agglutinates. It seems likely that this low agglutinate content is a consequence of the breakdown of the fragile, large agglutinates in the imported material during their movement to the sample site.