Barrier islands and cheniers are elongate, narrow sand bodies which may appear similar where preserved in the sedimentary record. However, their modes of origin and sequence of development are distinctive. Differentiation of these features is important in the interpretation of the depositional environments, paleogeography, and geologic history of coastal areas.

Chenier development begins with progradation by deposition of clay, silt, and sand. Rapid sedimentation precludes removal of fine material. Progradation is followed by reworking, shore retreat, and formation of a ridge at the head of the beach. Fines are transported seaward and along the shore. Sand is concentrated on the upper beach and over the adjacent marsh, and is transported along the shore, possibly accumulating in areas not actively eroding. The contact of the chenier with marsh and mud-flat deposits is disconformable beneath transgressive sand deposits, but may be intertonguing for laterally transported deposits. Increasing rates of sedimentation reinitiate mud-flat progradation and the sand ridge is left as chenier. Holocene cheniers are commonly less than 15 feet thick.

Barriers originate from a topographic ridge at the head of the beach which subsequently is partly submerged. Lagoonal-marsh sediments are deposited behind the barrier; however, continued subsidence accompanied by transgression may result in a complex intertonguing of barrier and lagoonal-marsh sediments. Barriers also form as spits and may develop seaward from a pre-existing barrier. Repeated spit formation results in the formation of sand bodies enclosed in finer sediments. Barriers, like cheniers, may be eroded, reworked, and moved landward over the adjacent marsh. Barriers predate the lagoonal-marsh sediments, whereas the sand ridge of the chenier develops on, and seaward from, existing marsh and mud-flat deposits.

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