alluvium
American Heritage Dictionary:
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al·lu·vi·um
(ə-lū'vē-əm) 
n., pl., -vi·ums, or -vi·a (-vē-ə).
Sediment deposited by flowing water, as in a riverbed, flood plain, or delta. Also called alluvion.
n., pl., -vi·ums, or -vi·a (-vē-ə).
Sediment deposited by flowing water, as in a riverbed, flood plain, or delta. Also called alluvion.
[Medieval Latin, flood, from neuter of Latin alluvius, alluvial, from alluere, to wash against. See alluvion.]
Oxford Dictionary of Geography:
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alluvium
A general term for all deposits laid down by present-day rivers, especially at times of flood. Alluvium is characterized by:
▪ sorting, so that coarser alluvium is found in the upper course of rivers and finer in the lower courses;
▪ stratification, such that coarse material in river bars is overlain by finer material;
▪ structures such as current bedding.
Alluvial landforms include alluvial cones and fans, deltas, river bed materials, and flood plains. Alluvial deposits are fertile, and can contain minerals, such as the alluvial gold and diamonds of West Africa. There is a tendency to restrict the term alluvium to fine-grained deposits such as silt or silty clays.
Gravel, sand, silt, soil, or other material that is deposited by running water.
Oxford Dictionary of Archaeology:
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alluvium
[Ge]
A general term for sediment deposited by rivers, including that on the river bed, along its margins, across its floodplain, and in an estuary, if it has one. Alluvium tends to be rich in organic matter and may contain archaeological material. The onset of periods of rapid alluviation may also have the effect of sealing old land surfaces under the alluvium.
Word Tutor:
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alluvium
IN BRIEF: n. - Clay or silt or gravel carried by rushing streams and deposited where the stream slows down.
Tutor's tip: "Alluvion" is the flow of water against a shore that sometimes deposits "alluvium" (silt or sand deposited by flowing water). When the wind deposits material such as sand or rock, the correct term is "eluvium."
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categories related to 'alluvium'
- Materials, Formations, and Substances - alluvium: clay, silt, sand, or gravel sediment deposited by running water
See crossword solutions for the clue Wikipedia on Answers.com:
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Alluvium
"Alluvial" redirects here. For the American racehorse, see Alluvial (horse). For the type of flow diagram, see Alluvial diagram.
Alluvium (from the Latin, alluvius, from alluere, "to wash against") is loose, unconsolidated (not cemented together into a solid rock) soil or sediments, which has been eroded, reshaped by water in some form, and redeposited in a non-marine setting.[1][2] Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. When this loose alluvial material is deposited or cemented into a lithological unit, or lithified, it would be called an alluvial deposit.
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Definitions
The term "alluvium" is not typically used in situations where the formation of the sediment can clearly be attributed to another geologic process that is well described. This includes (but is not limited to): lake sediments (lacustrine), river sediments (fluvial), or glacially-derived sediments (glacial till). Sediments that are formed and/or deposited in a perennial stream or river are typically 'not' referred to as alluvial.
Age
Most, if not all, alluvium is very young (Quaternary in age), and is often referred to as "cover" because these sediments obscure the underlying bedrock. Most sedimentary material that fills a basin ("basin fill") that is not lithified is typically lumped together in the term alluvial.
Ores
Alluvium can contain many valuable ores such as gold and platinum and a wide variety of gemstones. Such concentrations of valuable ores is termed a placer deposit.
See also
References
- ^ Glossary of Geological Terms. Geotech.org. Retrieved on 2012-02-12.
- ^ Geology Dictionary – Alluvial, Aquiclude, Arkose. Geology.Com. Retrieved on 2012-02-12.
External links
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Wikimedia Commons has media related to: Alluvium |
Chisholm, Hugh, ed. (1911). "Alluvium". Encyclopædia Britannica (11th ed.). Cambridge University Press.
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The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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A Dictionary of Geography. Copyright © Susan Mayhew 1992, 1997, 2004. All rights reserved.
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McGraw-Hill Dictionary of Architecture & Construction
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved.
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