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Very poorly sorted indicates that the sediment sizes are mixed (large variance); whereas well sorted indicates that the sediment sizes are similar (low variance). In the field, sedimentologists use graphical charts to accurately describe the sorting of a sediment using one of these terms. [1]
Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials . This is different from the crystallite size, which refers to the size of a single crystal inside a particle or grain.
Sorting describes the distribution of grain size of sediments, either in unconsolidated deposits or in sedimentary rocks. Very poorly sorted indicates that the sediment sizes are mixed (large variance); whereas well sorted indicates that the sediment sizes are similar (low variance). speleothem
Texture describes how rounded and sorted the sample is while composition describes how much the composition trends toward stable minerals and components (often quartz). A mature sediment is more uniform in appearance, for the sediment grains are well rounded, are of a similar size and exhibit little compositional variation.
Diagram showing well-sorted (left) and poorly sorted (right) grains. The size, form and orientation of clasts (the original pieces of rock) in a sediment is called its texture. The texture is a small-scale property of a rock, but determines many of its large-scale properties, such as the density, porosity or permeability. [17]
Conglomerates deposited in fluvial environments are typically well rounded and poorly sorted. Clasts of this size are carried as bedload and only at times of high flow-rate. The maximum clast size decreases as the clasts are transported further due to attrition , so conglomerates are more characteristic of immature river systems.
Immature stage: The sediment contains more than 5% clay and sand grains are poorly sorted and angular. Submature stage: The sediment contains less than 5% clay and sand grains are poorly sorted and subangular to subrounded. Mature stage: The sediment contains little to no clay and sand grains are well sorted but not well rounded.
In broad channels with decreasing slopes, slow-moving water can carry large amounts of detritus over a large area. Thus, graded beds form at points with decreased slopes in wide areas with less bounding of energy current flows. The energy is dispersed and decreases. Turbid sediments precipitate in concordant sizes and shapes in layers. [7]