Alluvium
Alluvium(fromLatinalluvius,fromalluere'to wash against') is looseclay,silt,sand,orgravelthat has been deposited by running water in a stream bed, on afloodplain,in analluvial fanorbeach,or in similar settings.[1][2][3]Alluvium is also sometimes calledalluvial deposit.[4][5]Alluvium is typically geologically young and is notconsolidatedinto solid rock.Sedimentsdeposited underwater, in seas,estuaries,lakes, or ponds, are not described as alluvium.[1] Floodplain alluvium can be highly fertile, and supported some of the earliest human civilizations.[6]
Definitions
[edit]The presentconsensusis that "alluvium" refers to loosesedimentsof all types deposited by running water infloodplainsor inalluvial fansor relatedlandforms.[1][7][8]However, the meaning of the term has varied considerably since it was first defined in the French dictionary ofAntoine Furetière,posthumously published in 1690. Drawing upon concepts fromRoman law,Furetière definedalluvion(the French term for alluvium) as new land formed by deposition of sediments along rivers and seas.[8]
By the 19th century, the term had come to mean recent sediments deposited by rivers on top of olderdiluvium,which was similar in character but interpreted as sediments deposited byNoah's flood.With the rejection by geologists of the concept of a primordial universal flood, the term "diluvium" fell into disfavor and was replaced with "older alluvium". At the same time, the term "alluvium" came to mean all sediment deposits due to running water on plains. The definition gradually expanded to include deposits in estuaries and coasts and young rock of both marine andfluvialorigin.[8]
Alluvium and diluvium were grouped together ascolluviumin the late 19th century. "Colluvium" is now generally understood to mean sediments produced by gravity-driven transport on steep slopes, while the definition of "alluvium" has switched back to an emphasis on sediments deposited by river action. There continues to be disagreement over what other sediment deposits should be included under the term "alluvium."[8]
Age
[edit]Most alluvium isQuaternaryin age and is often referred to as "cover" because these sediments obscure the underlyingbedrock.Most sedimentary material that fills abasin( "basin fill" ) that is notlithifiedis typically lumped together as "alluvial".[9]Alluvium ofPlioceneage occurs, for example, in parts of Idaho.[10]Alluvium of lateMioceneage occurs, for example, in the valley of theSan Joaquin River,California.[11]
See also
[edit]References
[edit]- ^abcJackson, Julia A., ed. (1997). "alluvium".Glossary of geology(Fourth ed.). Alexandria, Virginia: American Geological Institute.ISBN0922152349.
- ^Glossary of Geological Terms.Geotech.org. Retrieved on 2012-02-12.
- ^Geology Dictionary – Alluvial, Aquiclude, Arkose.Geology.Com. Retrieved on 2012-02-12.
- ^Jackson, Julia A., ed. (1997). "alluvial deposit".Glossary of geology(Fourth ed.). Alexandria, Virginia: American Geological Institute.ISBN0922152349.
- ^Allaby, Michael (2013). "alluvium".A dictionary of geology and earth sciences(Fourth ed.). Oxford: Oxford University Press.ISBN9780199653065.
- ^Kidder, Tristram; Liu, Haiwang; Xu, Qinghai; Li, Minglin (July 2012). "The Alluvial Geoarchaeology of the Sanyangzhuang Site on the Yellow River Floodplain, Henan Province, China: THE YELLOW RIVER FLOODPLAIN, HENAN PROVINCE".Geoarchaeology.27(4): 324–343.doi:10.1002/gea.21411.S2CID140587757.
- ^Allaby 2013,"alluvial".
- ^abcdMiller, Bradley A.; Juilleret, Jérôme (October 2020)."The colluvium and alluvium problem: Historical review and current state of definitions".Earth-Science Reviews.209:103316.Bibcode:2020ESRv..20903316M.doi:10.1016/j.earscirev.2020.103316.
- ^Chisholm, Hugh,ed. (1911)..Encyclopædia Britannica(11th ed.). Cambridge University Press.
- ^Ames, Dan (1998),"Formation of the Soils"(PDF),Soil Survey of Jerome County and Part of Twin Falls County, Idaho,Natural Resources Conservation Service,United States Department of Agriculture,p. 238
- ^Huber, N. King (1981).Amount and Timing of Late Cenozoic Uplift and Tilt of the Central Sierra Nevada, California—Evidence from the Upper San Joaquin River Basin (USGS Professional Paper 1197)(PDF).Washington D.C.:USGS.p. 13.
External links
[edit]
Media related toAlluviumat Wikimedia Commons
