Sorting describes the distribution of grain size of sediments, either in unconsolidated deposits or in sedimentary rocks. The degree of sorting is determined by the range of grain sizes in a sediment deposit and is the result of various transport processes (rivers, debris flow, wind, glaciers, etc.). 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.
Sorting Parameters edit
The terms describing sorting in sediments – very poorly sorted, poorly sorted, moderately sorted, well sorted, very well sorted – have technical definitions and semi-quantitatively describe the amount of variance seen in particle sizes.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]
Tangential sorting is the result of sediment being deposited in same direction as flow. Normal tangential sorting results in a gradient of sediment sizes deposited from largest to finest as they travel downstream[2]. When sediments are deposited from smallest to largest as they travel downstream, this is referred to as reverse sorting[2].
Rocks derived from well sorted sediments are commonly both porous and permeable, while poorly sorted rocks have low porosity and low permeability, particularly when fine grained.
Processes Involved in Sorting edit
Sediment sorting is influenced by: grain sizes of sediment, processes involved in grain transport, deposition, and post-deposition processes such as winnowing[3]. As a result, studying the degree of sorting in deposits of sediment can give insight into the energy, rate, and/or duration of deposition, as well as the transport process responsible for laying down the sediment[3].
Aeolian Processes edit
In reference to windblown sediment, a wide range of conditions such as distance and height of transport and varying wind patterns at the sediment source can affect grain size, rate of transport and distribution of sediment[3]. Windblown sediment travels one of three ways--rolling, saltation or suspension in the air.
Loess that is reworked by fluvial processes tends to have more poorly sorted sediment as compared to sediment sorted by only Aeolian processes because loess particles become mixed with preexisting sediment of varying grain sizes within bodies of water[3].
See also edit
References edit
- ^ Tucker, M.E., 1996, Sedimentary rocks in the field, John Wiley & Sons, Chichester, 153 p.
- ^ a b Kleinhans, M. G. (2004-03-01). "Sorting in grain flows at the lee side of dunes". Earth-Science Reviews. 65 (1): 75–102. doi:10.1016/S0012-8252(03)00081-3. ISSN 0012-8252.
- ^ a b c d Vandenberghe, Jef (2013-06-01). "Grain size of fine-grained windblown sediment: A powerful proxy for process identification". Earth-Science Reviews. 121: 18–30. doi:10.1016/j.earscirev.2013.03.001. ISSN 0012-8252.
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Peer Review goes in article talk page of person's sandbox draft. Start new discussion and put comments there.
Notes on Vandenberghe_2013 edit
- Transporting sediment with larger grain sizes is a more energetically intensive process that smaller grains, so they most often travel by rolling bc this requires least amount of energy. Transport is also influenced surface along which the grain is rolling and shape and texture of the grain's surface but to a lesser degree.
- Suspension requires stronger winds and air turbulence
- Sediment sorting is also influenced by conditions at the site of depositions such as annual precipitation.The Chinese Loess Plateau is one such formation that contains steppe vegetation, a sediment trap allowing for the formation of loess, and demonstrates a sorting pattern resulting from an accumulation of windblown sediment.
- Grain sizes up to 500 micrometers are typically saltated, while larger grains which range up to several millimeters are typically transported by rolling.
- Fluvial, glacio-fluvial processes -> transport by water, glaciers, etc.
Folk and Ward 1957- include section on sorting parameters, summarize foundation of measurement convention.
Say that they that it is a seminal paper that defines the parameters.
Purpose of studying sediment transport is to determine the direction of transport
Notes on Kleinhans 2004 edit
Article Evaluation edit
Most of the article contains information that is relevant to the topic. I also think the page could generally be better organized by separating the information that is currently there into different sections because at the moment there are not clear transitions between changes in subtopics. A useful addition might expanding on how the forces involved in sorting (wind, rivers, earthquakes, etc.) influence what classification of sorting is left behind. Also mentioning the different formations that can arise from different types of sorting or how this affects landscapes and biota could be valuable. The information presented so far is pretty clear, easy to understand, and accurate.
There is a brief note of clarification about a similar topic (crystallites) but it is placed at the top of the page, right below where the topic is defined. I think this is poor placement because while it could be a helpful distinction, it's placement is distracting and implies undue importance to the topic.
The tone of the article is neutral and I don't detect any bias in any of the claims or viewpoints.
The links to the citations work, but only two claims in the article have a source cited for them. A source has not been cited for much of the relevant information. The sources seems to be neutral and apt for the topic, but both citations also appear to come from books that were published before the year 2000, making them possibly outdated and difficult to obtain for verification of their quality.
No conversations have occurred on the Talk page of this article so far, but it has been added to the Geology WikiProject. It is currently rated as a stub.
***Note to self: put topic into chatGPT to get ideas for directions in which to expand on the topic
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