Sediment Grain Size Distribution Research Articles

Distribution of western beaufort sea polychaetous annelids

Depth and depth-related processes appear to exert primary control over the distributional patterns of species of polychaetous annelids in the western Beaufort Sea (Cape Halkett to Barter Island, Alaska). Species richness and total polychaete abundance are maximal along the outer continental shelf and upper continental slope. Stations exhibiting the most similar polychaete assemblages are located at similar depths. However, some species distributions appear to correlate better with sediment type than with depth. Maximum abundance occurs deeper on the continental slope to the west, and station clusters generated by non-hierarchical clustering (using the dominant polychaete species data) are not sorted strictly by depth. In a canonical analysis of discriminance, the station clusters were projected onto a two-dimensional plane in “species space”. The first and second canonical variables of the station clusters correlate with sediment grain-size distributions, suggesting a relationship between polychaete distribution patterns and the sedimentary environment. This relationship is further substantiated when sediment grain-size distributions for each station are plotted on a tertiary diagram: the stations are grouped and ordered in a pattern similar to that generated by the canonical analysis of discriminance.

An oblique factor analysis solution for the analysis of mixtures

The problems involved in the factor analysis of data consisting of measurements of material quantity or proportion are discussed, and the inability of existing factor analysis solutions to properly model such data is pointed out. A new factor analysis solution using the linear programming technique is presented which properly analyzes mixture data. A numerical example is presented in which a body of suspended sediment grain-size distribution data is analyzed using the new factor analysis solution. FORTRAN-IV subroutines for computing this solution are included in an Appendix.

GRAIN SIZE DISTRIBUTIONS OF SURFACE SEDIMENTS OF THE YAHAGI RIVER ALLUVIAL PLAIN

The author has reported, recently in this journal (Moriyama, 1977), a study on the grain size distributions of surface sediments of the Kiso River alluvial plain which exemplyfied Japanese alluvial plains. In this report, standing on the similar viewpoint to the previous report, he firstly clarifies the relationship between landforms and grain size distributions of the Yahagi River alluvial plain sediments, and then give final explanation of all analyzed results by him (Moriyama, 1976b, 1977). Fig. 1 shows the landforms of the Yahagi River alluvial plain and a distribution of sampling points of sediments. Table 1 lists the statistical parameters (calculated by moment method), of all samples and Fig. 2 illustrates a correlation diagram between the mean and skewness of the statistical parameters. In this figure the plots of river sands are clearly distinguished from those of flood plain sediments; however each muddy sediment can not be distinguished individually, i.e., YN and YB overlap each other. A strong negative correlation between the mean and skewness can be seen in this muddy sediments as for those of the Kiso River alluvial plain. In order to consider precise sedimentological meanings of the muddy sediments, firstly the author drew the cumulative grain size distribution curves on normal probability graph paper for all samples (Figs. 3_??_5). Then, he segregated quantitatively each curve into several component populations, each having the normal distribution and calculated the mean, standard deviation and mixing proportion for each component population employing the method developed by Inokuchi & Mezaki (1974). Distributions of mean, standard deviation and mixing proportion for each component population are shown in Fig. 6. All samples are composed of two to four component populations and can be grouped into sand-gravel and clay populations, lacking component populations in silt size. The sand populations are well sorted while the clay populations are of relatively poor sorting. Using the averaged frequency of all size classes for each geomorphic element, histograms and relative frequency distribution curves were constructed as shown in Fig. 7, in which also included were the analyzed samples for the Kiso River alluvial plain sediments and deltaic shallow marine bottom sediments in the northwestern Mikawa Bay. Generally, the shapes of frequency distributions of all geomorphic elements except for sandy deposits show common features of bimodal distributions and reveal a “valley” around 5 phi. Comparing the shapes of histograms of the Kiso River alluvial plain sediments with those of the Yahagi, we can recognize a common “shoulder” at 0_??_2 phi in YN and YB, and even in SMp, while IF, KN and KB have no “shoulder” at O_??_2 2 phi. This implies that the size characteristics of the sand population can be attributed to that of the original materials from which sediments are supplied to the alluvial plain. Larger grain size of the Yahagi River alluvial plain sediments are thought to be caused by the coarser-grained granitic rocks of the drainage basin. Relative frequencies of the sand population decrease in the order of, IF>KN>KB, and YN>YB. The author's conclusive explanations can be summarized as follows; As clay populations show fairly consistent characteristics in all geomorphic elements, it might be produced originally by weathering processes active in the weathered mantle of mountain and hill slops, not by hydraulic conditions. On the other hand, the size characteristics of sand population are basically affected by the grain size distribution of rock-forming minerals in the drainage basin rather than by hydraulic conditions at flood deposition. The mixing proportions of sand population, however, are considered to be determined by the intensity of flood flows.

Land Classification and Development of the Sendai Coastal Plain

The Sendai Coastal Plain is located in the northeastern part of Honshu Island. The studied area in this paper is the southern part of this coastal plain and is about 30km long from north to south and 8km wide from east to west. Natural levees, beach ridges and other micro-landform units are commonly recognized in this area, but in place exist some landform units with slight elevation which can not be classified into either natural levee or beach ridge according to their similar topographic forms. The present author attempted to discriminate these uncertain landform units into natural levee or beach ridge from statistical parameters which depend on the shape of grain size frequency curves.For this purpose the author first of all clarified from the grain size distributions of sediment on typical natural levees and beach ridges, that standard deviation versus skewness and standard deviation versus mean grain size are effective in distinguishing the sediment of natural levee from that of beach ridge (Figs. 3, 4). The beach ridge sand and the natural levee sand are mainly separated by standard deviation, that is to say, beach ridge sand is more sorted than natural levee sand. And these sands are much more distinguishable by an analysis of the relation between standard deviation and other parameters of skewness and mean grain size.As the result of land classification, with consideration of sedimentary structures of alluvium and distribution of historical remains, the geomorphological development of this coastal plain was considered as follows (Figs. 8, 9).i) About 7, 500yrs. B. P. this area was under shallow maritime environment and the shore line was indented into the hilly area.ii) And by the beginning of the Yayoi period (about 2, 000yrs. B. P.), the 1st (innermost) beach ridge in this area was formed along the foot of hill-land, which resulted in shallowing of sea bottom by deposition of the terrestrial sediment, according to the reduced rate of sea level rise.iii) The 2nd beach ridge range appeared on the shallow off-shore bottom, before the middle Kohun period (about 1, 500yrs. B. P.), following to accmulation of terrestrial sediments on sea bottom. The marsh between 1st and 2nd beach ridges was gradually filled by fluvial sediment and peaty sediment, and the later period of this stage, the natural levee, to the north of Abukuma river, was formed on the marsh.iv) The 3rd beach ridge range was formed near the present shore line in the last stage. The marsh formed between 2nd and 3rd beach ridges was gradually accumulated and modified by natural levees while the Abukuma river changed its course due to repeated floodings and cut the 2nd beach ridge, then the natural levee, to the south of the river, was formed.

PHi Mean and Phi Standard Deviation of Grain-size Distribution in Sediments: Method of Moments

ABSTRACT Adding (or subtracting) a constant to a group of observations results in adding (or subtracting) the same constant to the arithmetic mean but will not change the standard deviation. This provides a convenient statistical manipulation that permits simplification of the computation procedure of statistical parameters of grain-size distribution of sediments. The phi mean and phi standard deviation (and also skewness and kurtosis) are computed directly from the sieve screen size and weight frequencies.

Comparison of measured and predicted nearshore sediment grain-size distribution patterns, southwestern Lake Michigan, U.S.A.

Comparison of calculated grain sizes with those found in a part of the shoaling zone of south western Lake Michigan reveals that existing quantitative expressions yield sizes which are much larger than those of the natural sediments, but that many aspects of the pattern of size distribution are predictable. An empirical and a theoretical expression were each used to calculate grain sizes in equilibrium with several different wave states for the measured bathymetry. For each wave state, the theoretical equation yields sizes which are closer to those found in the field over most of the shoaling zone, but sizes predicted by each of the two equations approach each other as the shore is approached and natural slopes increase toward the slope used in formulating the empirical expression. Grain-size trends predicted by the calculations include coarsening toward shore and to the south near shore. The calculations with the theoretical expression reveal more detail and predict an anomalously coarse area in the deeper part of the field area and elongate areas of fine sediments close to shore. Some support for the existence of these areas was found in the field.

Texture of River and Beach Sediments Seaward from Active Volcanic Highlands, Southwestern Guatemala: ABSTRACT

Sedimentologists have investigated grain-size distributions of sediments from various environments in an attempt to gain uniformitarian insight for reconstruction of ancient environments. However, modern river and beach sediments occurring seaward from active volcanic highlands have been little studied even though ancient analogues may be common locally. The Pacific coastal plain in Central America is widest in Guatemala where it is abruptly terminated 10-30 mi inland by the steep slopes of a row of active Quaternary volcanoes. The slopes are locally bare of vegetation, and the strongly seasonal, torrential rainfall provides abundant bed load to low-sinuosity streams that discharge onto the coastal plain and flow seaward in a roughly parallel pattern. Guatemala river and beach-face sands are mostly moderately to moderately well sorted (river average ^sgrI = 0.87^phgr units; beach average ^sgrI = 0.54^phgr units), near symmetrical, mesokurtic, medium-grained (river average Mz = 1.44^phgr; beach average Mz = 1.45^phgr) volcanic arenites, composed predominantly of unweathered grains of angular volcanic rock fragments, plagioclase, and ferromagnesian and opaque minerals. River sands can be distinguished from beach sands by plotting mean size versus sorting, by coarsest percentile (C) versus median percentile (M), and by inspection of cumulative probability curves. Curves for river sands commonly show subpopulations inferred to reflect sliding and/or suspension populations. Saltation populations, in both river and each sands, are usually polymodal because of mixing of grain populations differing in specific gravity and shape. Published bivariant plots and other techniques are assessed in terms of the Guatemalan sands. End_of_Article - Last_Page 634------------

"Comparison of the descriptors of sediment grain-size distributions" by T. A. Jones; a discussion

For reference to paper under discussion, see this Bibliography Vol. 35, No. 2, 17 E71-04051

Sediment microbiology and grain-size distribution, as related to tidal movement, during the first mission of the West German Underwater Laboratory ?Helgoland?

During the first 3 week mission of the Underwater Laboratory (UWL) “Helgoland”, July 28 to August 19, 1969, near Helgoland, North Sea, in situ studies were conducted on the bottom water and sediment microflora. The number and species composition of bacteria of the bottom water and sediments was influenced by (a) microtopographical conditions; (b) local changes in tidal currents; (c) artificially introduced changes of the bottom environment. During the UWL experiments comparisons were made of samples taken by conventional methods from R.V. “Friedrich Heincke” and hand samples taken by aquanauts. The process of hauling aboard to Van-Veen grabs and box samplers invariably changes the structure of the uppermost millimeters of certain sediments. These changes manifest themselves in reduction of bacteria numbers as well as in values obtained for water content and organic matter. Obviously, in ship collections, the uppermost layer of the sediment samples loses bacteria, water and organic matter to the supernatant water and to the lower parts of the sample due to water movement and to consolidation affected by sampling processes. Changes in sediment structure and composition do not cause immediately recordable variations in total numbers of bacteria; however, they are followed by changes in relative abundance of specific groups of bacteria (e.g. sulfate reducers). These facts suggest that sediment transport does not mechanically damage the microflora, but that resulting changes in sediment structure and grain-size distribution are followed by a more or less fast redistribution of the microflora.

Comparison of the Descriptors of Sediment Grain-Size Distributions: REPLY

Comparison of the Descriptors of Sediment Grain-Size Distributions: REPLY

Environmentally significant sedimentologic characteristics of beach sands

Abstract Comparative study of five South Island beaches and a beach on the central Texas coast suggests a short list of features that are diagnostic of the coastal beach. Beach sediments are clean (no mud matrix) and are very well to moderately well sorted. Foreshore strata occur as even, internally laminated, thin beds that dip seaward at low angles. The angle of dip is directly related to the slope of the foreshore surface (especially the beach face), which in turn is largely dependent upon the mean size of the beach sediment, that is, the coarser the grain size the steeper the foreshore. Backshore strata occur as lens- and slightly wedge- shaped, internally laminated thin beds. Scour surfaces and cross-stratified lenses are characteristic. Dip of strata varies from 0° to 15°, and strata dip directly or obliquely landward. A transition zone (foreshore or above high tide level plus outer backshore) is characterised by mixed foreshore and backshore stratification, and some strata dip landward, others dip seaward. Contrary to the widely held view that grain size distributions of beach sediments are negatively skewed, many beaches furnish positively skewed distributions. We conclude that skewness is not necessarily an environment-sensitive measure, and that skewness values commonly reflect grain size characteristics inherited from the source rocks.

Diffusion and Settling of Suspended Sediment at River Mouths: a Computer Simulation Model: ABSTRACT

A Fortran IV computer program has been written for simulating the diffusion and settling of suspended sediment at river mouths. The rate of sediment accumulation at any point in front of the channel mouth is governed by water and sediment discharge, sediment grain-size distribution, sediment density, the porosity of the resulting sediment, width and depth of the river channel, and the geometry of the basin. A plane jet model is used for determining the velocity field and the rates of sediment diffusion. By adjusting the input parameters, a variety of deposits may be created. The shape and foreset slope of the delta fan are found to be closely controlled by grain size and discharge. By allowing the model to respond dynamically to the buildup of sediment at the chan el mouth, a distributary mouth bar and submerged levees can be formed. Delta-simulation experiments are monitored by printing (1) maps showing the rates of sedimentation for each grain size at every point in a digital accounting grid and (2) facies maps using alphabetic symbols. Maps and stratigraphic cross sections are drawn with a digital plotter. Computer simulation is an important method for sedimentology, and should be used in combination with hydraulic models and direct observations of natural phenomena. End_of_Article - Last_Page 2162------------

The Types of Grain Size Distribution in Shallow Sea Sediments

The Types of Grain Size Distribution in Shallow Sea Sediments

Mesozoische und gegenwärtige Korngrößenverteilung und ihre Beziehungen zum Sedimentationsraum

Mesozoische und gegenwärtige Korngrößenverteilung und ihre Beziehungen zum Sedimentationsraum