Deltaic Deposits

deltaic deposits

[del′tā·ik di′päz·əts]
Sedimentary deposits in a delta.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Deltaic Deposits


deposits of river drift in seas and lakes at the mouths of rivers. The cause of deposition is a sharp drop in water flow rate and partly in the coagulation of the fine particles brought by the river in suspension or as colloidal solutions upon encountering salt water. Favorable conditions for formation of thick layers of deltaic deposits include the absence at the mouths of the rivers of significant wave action and currents, which could carry away river drift, and a slow, steady sagging of the particular area of the earth’s crust. Deltaic deposits up to several kilometers thick can form under such conditions. The accumulative formation caused by deltaic deposits, the delta, is built up from the surface primarily by river and lacustrine-swamp sediment. The sediment of shallow parts of the sea, which have been desalinized by river waters, as well as lagoon and bar deposits, are part of deltaic deposits.

Deltaic deposits consist mainly of arenaceous-argillaceous rocks with occasional intercalations of limestones, less frequently of coal and other rock of organic origin; conglomerates are often found in piedmont regions. Deposits of coal and iron and copper ores are found in deltaic deposits. Fertile soils generally form on deltaic deposits characterized by a fine-grained nature and diversity of composition. Because of this, the deltas became centers of the farming culture and were densely populated even in the distant part (for example, the Nile delta). Deltaic deposits are also often encountered in the fossil state in sedimentary strata of past geological periods. They are usually characterized by considerable thickness, uniqueness of structure (such as the presence of definite types of cross bedding), and the combination of various marine, brackish-water, and continental deposits.


Del’tovye i melkovodno-morskie otlozheniia. [Sb. st.]. Moscow, 1963.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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Glacial, glaciofluvial, and deltaic deposits near the eastern limit of Illinoian ice (Forsyth 1966; Pavey and others 1999) at Hanover locally filled the Deep Stage Newark valley to an elevation of 275 m (900 ft) (Pavey 1995; see also early discussions by Leverett 1902 and Carney 1907).
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Much of the area consists of unconsolidated deltaic deposits comprising substantial thicknesses of clays, granular soils, and silty clays within buried channels and lenses.
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