alluvium

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alluvium

a fine-grained fertile soil consisting of mud, silt, and sand deposited by flowing water on flood plains, in river beds, and in estuaries

Alluvium

 

or alluvial deposits. (1) Deposits of fluvial water courses—rivers, streams—forming floodplains and terraces of river valleys. They play a very important role in the structure of most continental sedimentary formations. The alluvium of plains rivers (see Figure 1) usually combines fluvial alluvium deposited in the migrating bed (obliquely laminated sands and gravel), floodplain alluvium which accumulates on the fluvial during floods (mainly loams and sandy loams), and oxbow-lake alluvium which settles in the oxbow-lakes (mainly sandy loams and loams which are rich in organic matter).

Figure 1. Diagram of structure of alluvium from plain river: (1) fluvial alluvium, (2) floodplain alluvium, (3) oxbow-lake alluvium, (4) bedrock from slopes and bottom of river valley, (5) water level during flooding.

The composition and structure of the alluvium differ substantially depending on the size and hydraulic regime of the flow, the relief of the drainage system, and the rock composing it. For example, in the alluvium of mountain rivers, there is a predominance of boulder and pebble fluvial alluvium; streams which flow through ravines and gullies deposit poorly graded alluvium in which it is difficult to distinguish the fluvial, floodplain, and other types of alluvium. In ancient sedimentary beds, the alluvium is usually cemented together and composed of hard fragmented rock such as conglomerates, sandstones, argillites, and so forth. The fluvial alluvium may contain placers of gold, platinum, and other useful minerals in addition to deposits of construction sands and gravel.

(2) In foreign literature, alluvium is the name often given to any deposits of running waters, including proluvium and deluvium.

(3) The obsolete name of all recent continental deposits formed in the postglacial age (Holocene); the term “alluvium” is sometimes used in this sense only in German literature.

REFERENCES

Shantser, E. V. Alluvii ravninnykh rek umerennogo poiasa i ego znachenie dlia poznaniia zakonomernostei stroeniia i for-mirovaniia alliuvial’nykh svit. Moscow, 1951.
Shantser, E. V. Ocherki ucheniia o geneticheskikh tipakh. kontinental’nykh osadochnykh obrazovanii. Moscow, 1966.

E. V. SHANTSER

alluvium

[ə′lüv·ē·əm]
(geology)
The detrital materials that are eroded, transported, and deposited by streams; an important constituent of shelf deposits. Also known as alluvial deposit; alluvion.

alluvium

Gravel, sand, silt, soil, or other material that is deposited by running water.
References in periodicals archive ?
High fractal dimension is the result of tectonic activities that causes to formation of loose alluvial deposits and irregularities possess high fractal lower fractal dimensions.
The groundwater aquifers in the area are the weathered basement and the Alluvial deposits of the wadis.
Chromium appears to be enriched in the alluvial deposits, while Co, Pb, and Zn show concentrations higher than the Earth's crust (enrichment factors between 1.3 and 1.9) (Table 1).
The geoelectrical ERT-P1 section includes a thin layer of alluvial deposits which covers the first third of the section.
Most plants growing in alluvial deposits along the Rio Grande and adjacent terrace deposits on hillsides and in arroyos (Geologic Atlas of Texas, Marfa Sheet, 1979) occur in a variety of microhabitats in the Chihuahuan Desert.
Artisanal diamond mining in alluvial deposits along river banks consists of informal digging with basic equipment (often with unprotected hands and feet).
The recovery of the 189.6-carat stone is compatible with our statistical predictions that diamonds of greater than 100 carats in size are an inherent part of the diamond population found in these unique alluvial deposits. Four plus 100 carat stones have now been recovered from the site.
The main topics are (1) the geomorphological features of the plain, as detected by micro-landform interpretation, (2) the relationships between these geomorphological features and floods, and (3) the subsurface geology of the plain, especially with regard to alluvial deposits of the Mekong.
New correlations are developed for alluvial deposits of Surat and SUDA using laboratory results shown in Table 3.
To save the wall, engineers will have to sink piles down to the bedrock 18 metres under the alluvial deposits and put in concrete columns built into wall.
The second are alluvial deposits, where erosion over millions of years has washed away some and deposited others across river beds and flood plains.
According to the above mentioned, the cartography to scale 1:25000 of Quaternary Coluvio Alluvial Deposits inside corridors of Silvia Pijao and Cordoba faults between the municipalities of Calarca and Pijao (Quindio), at Cordillera Central's West Mountain Front of Colombia produced.