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).
What does sorting mean in geology?
1. n. [Geology] The range of sedimentary grain sizes that occurs in sediment or sedimentary rock . The term also refers to the process by which sediments of similar size are naturally segregated during transport and deposition according to the velocity and transporting medium.
What causes well sorted sediment?
Well-sorted sediments have grains of similar size, and are the result of much sediment transport and earth processes which segregated the sediment by depositing different size fractions in different places . ... Other examples of angular, poorly-sorted rocks are breccia and arkose sandstone.
How does sorting affect porosity?
Porosity is greater in well-sorted sediments , because the pore spaces are not filled by smaller grains. ... Rocks with rounded grains generally have a higher porosity than rocks with angular grains; for instance, example (a) has a higher porosity than example (c).
Where are well sorted sediments found?
Beach sediments that have been transported great distances will be sorted according to grain size. For example, Gulf coast sediments may have traveled the length of the Mississippi River. Winnowing of more uniform sediment shapes and sizes results in a beach with well-sorted sediments.
How does sorting occur?
Sorting – The degree of uniformity of grain size. Particles become sorted on the basis of density , because of the energy of the transporting medium. High energy currents can carry larger fragments. ... Sorting gives clues to the energy conditions of the transporting medium from which the sediment was deposited.
What is size sorting?
Sorting describes the distribution of grain size of sediments , either in unconsolidated deposits or in sedimentary rocks. This should not be confused with crystallite size, which refers to the individual size of a crystal in a solid. Crystallite is the building block of a grain. ... See Grain size § Sorting for details.
Is siltstone well sorted?
*Characteristics – fine-grained siltstone and shale, which are well stratified (layered) commonly, form in the central portion, whereas some well-sorted sandstone is also formed along the margins.
Is Sandstone well sorted or poorly sorted?
Mature sandstones are clay-free, and the sand grains are subangular, but they are well sorted —that is, of nearly uniform particle size.
Which sediments are better sorted?
Description. Sorting can reflect both sediment source and/or transport, with aeolian-transported sediments being among the best sorted and glacial sediments being among the poorest sorted.
What is the difference between porosity and permeability?
More specifically, porosity of a rock is a measure of its ability to hold a fluid. ... Permeability is a measure of the ease of flow of a fluid through a porous solid. A rock may be extremely porous, but if the pores are not connected, it will have no permeability.
What factors do not affect porosity?
Interestingly, grain size does not affect porosity. For example, consider a box filled with spherical particles packed as tightly as possible.
How does sorting affect permeability?
Permeability decreases as the degree of sort- ing varies from good to poor because small grains can fill the spaces between large grains. Permeability is also influenced by grain shape. ... Consequently, the spaces between grains and the cross-sectional areas open to flow decrease, leading to lower permeability.
What are the two types of glacial deposition?
Glacial Drift: material deposited by a glacier. Two types of drift are Till (unsorted, unstratified debris deposited directly from ice) and Stratified Drift (sorted and stratified debris deposited from glacial meltwater).
Is till well sorted?
Glacial till, which contains a mixture of course angular rock fragments, sand, silt, and mud is a good example of poorly -sorted sediment . Fluvial processes include the motion of sediment and erosion or deposition of a sediment. Fluvial processes can have well-sorted and poorly-sorted sediment.
Are moraines well sorted?
Moraines are formed of the sedimentary materials of varying sizes. Accordingly, they are poorly sorted and are essentially the sedimentary “dump” of material broken, dislodged, smashed, ground, and then deposited during the movement of glaciers .
