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 ?
In order to delineate variations of the alluvial deposits thickness at the wadis sites the best geophysical techniques to be employed are the electrical or electromagnetic methods because of the electrical contrasts between conductive over-bank deposits and the resistive coarse-grained sediments in the inner wadis as well the contrast between the higher resistive basement rocks and the overlying saturated zone of weathered basement and the alluvial deposits which are overlain by more resistive dry superficial deposits.
Soil sampling was carried out by removing the grass roots and vegetation from the depth of 25 cm to 50 cm to obtain the intact samples from the alluvial deposits.
The derived correlations for alluvial deposits of Surat SUDA are tabulated in Table 4.
Discharges from placer mining consist of water and the naturally occurring materials found in alluvial deposits.
The geothermal reservoirs are located within volcanic rocks buried beneath alluvial deposits.
The rich onshore alluvial deposits in the Namib desert between the Orange River and the Namibian port of Luderitz have yielded over 70m carats of high quality gems since World War One.
This is particularly valuable where, as is usually the case with alluvial deposits, grade and ore characteristics vary rapidly both along and across the channels and sampling data ahead of the plant are inadequate.
The Company's operating model is an attractive alternative for smaller mines with alluvial deposits, and as a result, Casablanca has many options to deploy its asset in various mining regions around Chile.
The Company's wholly-owned Mozambican subsidiary, Explorator, has today appointed the Mining Contractor, who will have the exclusive right to mine the O block of the western half of the unconsolidated alluvial deposits on the Permitted Area of the Mining Concession area.
Approximately 7 mt of gold were produced last year, mostly by an estimated 40K or more "informal" miners illegally working alluvial deposits alone, or as part of loosely organized "cooperatives" that have been granted concessions and are run by local businessmen.
He discusses the different types of dredge and goes on to explain why he thinks that a bucket-line dredge should always be used on alluvial deposits.
60m minimum diameter inside) located in the alluvial deposits of the rhne and in the water table - 2 wells of 10 to 20 m in diameter and 15m deep - connecting structures at both ends of the structure - access stairs, doors and hatches, as well as lighting and ventilation - 2 circuits of high-voltage copper cables with xlpe insulation of 1~350m in a single length (without junction in the tunnel), with a cross-section of between 800 and 2,500 mm2 (1 or 2 cables per phase).