Winnowing (sedimentology)
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sedimentology Sedimentology encompasses the study of modern sediments such as sand, silt, and clay, and the processes that result in their formation (erosion and weathering), transport, deposition and diagenesis. Sedimentologists apply their understanding of mo ...
, winnowing is the natural removal of fine material from a coarser
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand an ...
by wind or flowing water. Once a sediment has been deposited, subsequent changes in the speed or direction of wind or water flowing over it can agitate the grains in the sediment and allow the preferential removal of the finer grains. This action can improve the
sorting Sorting refers to ordering data in an increasing or decreasing manner according to some linear relationship among the data items. # ordering: arranging items in a sequence ordered by some criterion; # categorizing: grouping items with similar pro ...
and increase the mean
grain size 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 refer ...
of a sediment after it has been deposited.Compton, R. R., 1962, Manual of field geology, John Wiley & Sons, 378 p. The term ''winnowing'' is from the analogous process for the agricultural separation of wheat from chaff.


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{{Wiktionary-inline, winnowing Sedimentology Separation processes