Reference Work Entry

Beaches and Coastal Geology

Part of the series Encyclopedia of Earth Science pp 398-398

Estuarine delta

  • Lynn D. Wright

The term estuarine delta refers to subaqueous and subaerial deltaic deposits that have accumulated within the semiconfined and protected environment of an estuary. At least two genetically and morphologically distinct types of estuarine delta may be recognized: deltas wholly or partially filling open-ended, funnel-shaped estuaries; and deltas wholly or partially filling barrier lagoons or estuaries impounded by coastal barrier formations. Estuarine deltas of the first type are best developed in macrotidal environments where bidirectional tidal currents redistribute river-derived sediments. Deposits assume the form of elongate, subaqueous tidal ridges, subaerial midchannel islands, and shoals and tidal flats. Examples include the Ord, Fly, Colorado, and Amazon deltas (Wright, 1978; Wright, Coleman, and Thom, 1975).

Estuarine deltas of the second type are typically fluvially dominated accumulations formed within shallow estuaries that are shelt ...

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