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 sediments. Rapid sedimentation precludes removal of fines. Progradation is followed by a period of reworking, shore retreat, and formation of a ridge along the landward side of the beach. Fines are transported seaward and along the shore. Sand is concentrated on the upper beach and on top of the adjacent marsh and is transported along the shore; it may accumulate in areas not being actively eroded. The contact of the chenier with underlying marsh and mudflat deposits is disconformable in areas of reworking and shore retreat, but the chenier may intertongue with finer sediments where the sand has been transported laterally along the shore. A return of conditions favoring rapid sedimentation reinitiates m dflat progradation and the sand ridge is left as a chenier. Holocene cheniers are commonly less than 15 ft thick.

Barriers originate from a topographic ridge along the landward side of a beach which subsequently is partly submerged. Lagoonal-marsh sediments are deposited behind the barrier; however, continued submergence accompanied by transgression may result in complex intertonguing of barrier and lagoonal-marsh sediments. Barriers also form from spits, but this is not believed to be the general mechanism of barrier formation. Barriers, like cheniers, may be eroded, reworked, and moved landward over the adjacent marsh. Generally, barriers predate the lagoonal-marsh sediments, although, with continued submergence, synchronous deposition may occur. The sand ridge of the chenier develops on, and seaward of, existing marsh and mudflat deposits.