Deltaic Deposits

deltaic deposits

[del′tā·ik di′päz·əts]
(geology)
Sedimentary deposits in a delta.

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.

REFERENCE

Del’tovye i melkovodno-morskie otlozheniia. [Sb. st.]. Moscow, 1963.
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References in periodicals archive ?
The Slagle delta is the largest of four deltas that laterally coalesce and have deltaic deposits up to .
Deltaic and alluvial deposits of the Bom Jardim Formation can be observed in the CQP-02RS well, whereas the CQP-03-RS well only comprises deltaic deposits of the same formation.
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).
Black Hand Gorge State Nature Preserve: Lower Mississippian deltaic deposits in east-central Ohio.
The river slows as it reaches the gulf because of the tides pushing upstream; as it slows down, it spreads out and delivers much of its sediment load into deltaic deposits.
Some of these showed low pollen concentrations, which could indicate the difficulties of working with some of the deltaic deposits.
Character and growth of deltaic deposits in Lewisville Lake, Texas.
In comparison to sedimentation on the floor of reservoirs, relatively little attention has been paid to the growth rate, morphology, and composition of these deltaic deposits.
The deltaic deposits also extend some four miles upstream from the estimated position of the original reservoir shoreline (assumed to coincide with the 515-foot elevational level on the predelta surface--Fig.