Lacassine national wildlife refuge Louisiana

A chenier or chénier is a sandy or shelly

beach ridge A beach ridge is a Ocean surface wave, wave-swept or wave-deposited ridge running parallel (geometry), parallel to a shoreline. It is commonly composed of sand as well as sediment worked from underlying beach material. The movement of sediment ...

that is part of a

strand plain A strand plain or strandplain is a broad belt of sand along a shoreline with a surface exhibiting well-defined parallel or semi-parallel sand ridges separated by shallow Swale (landform), swales. A strand plain differs from a barrier island in ...

, called a “chenier plain,” consisting of cheniers separated by intervening mud-flat deposits with marsh and swamp vegetation. Cheniers are typically one to six meters high, tens of kilometers long, hundreds of meters wide, and often wooded. Chenier plains can be tens of kilometers wide. Cheniers and associated chenier plains are associated with shorelines characterized by generally low wave energy, low gradient, muddy shorelines, and abundant sediment supply. The name is derived from the Louisiana French word for these formations, “chênière", meaning oak-grove, referring to the forests of live oaks

Quercus virginiana ''Quercus virginiana'', also known as the southern live oak, is an evergreen oak tree endemic to the Southeastern United States. Though many other species are loosely called live oak, the southern live oak is particularly iconic of the Old South. ...

that occupy the chenier ridges within southwest Louisiana.Goodie, A.S. (2004) ''Encyclopedia of Geomorphology'' Routledge. London, United Kingdom. 1,200 p. Otvos, E.G. and W.A. Price (1979) ''Problems of chenier genesis and terminology—an overview.'' Marine Geology. v. 31, pp. 251–263.

Colorado River Delta

Cheniers made primarily of shells of the Colorado Delta clam are found in the

tidal flats Mudflats or mud flats, also known as tidal flats or, in Ireland, slob or slobs, are coastal wetlands that form in intertidal areas where sediments have been deposited by tides or rivers. A global analysis published in 2019 suggested that tidal ...

of the

Colorado River Delta The Colorado River Delta is the region where the Colorado River once flowed into the Gulf of California (also known as the Sea of Cortez) in eastern Mexicali Municipality in the north of the state of Baja California, in northwestern Mexico. The ...

in northeastern

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

.Kowalewski, M., and K.W. Flessa (1995
''Comparative taphonomy and faunal composition of shelly cheniers from northeastern Baja California, Mexico.''
Ciencias Marinas. v. 21, no. 2, pp. 155-177.

Louisiana

The Louisiana Chenier Plain, extending roughly from

Sabine Lake Sabine Lake is a bay on the Gulf coasts of Texas and Louisiana, located approximately east of Houston and west of Baton Rouge, Louisiana, Baton Rouge, adjoining the city of Port Arthur, Texas, Port Arthur. The lake is formed by the confluence ...

to Vermilion Bay along the Gulf Coast, serves critical ecosystem functions, particularly as a wildlife habitat and stopover for migrating birds. As the region was settled, the cheniers were developed preferentially, owing to protection from flooding afforded by the higher elevation. Examples of communities situated on such ridges in the Chenier Plain include Grand Chenier in Cameron Parish, Pecan Island in Vermilion Parish and the former settlement of Cheniere Caminada adjacent to Grand Isle, south of

New Orleans New Orleans (commonly known as NOLA or The Big Easy among other nicknames) is a Consolidated city-county, consolidated city-parish located along the Mississippi River in the U.S. state of Louisiana. With a population of 383,997 at the 2020 ...

. The ridges, however, offer insufficient protection from storm surges, thus Cheniere Caminada was completely destroyed by a hurricane in 1893, and Pecan Island and Grand Chenier have been devastated by several powerful storms, including

Hurricane Audrey Hurricane Audrey was one of the deadliest hurricanes in U.S. history, killing at least 416 people as it devastated the southwestern Louisiana coast in 1957. Along with Hurricane Alex (2010), Hurricane Alex in 2010 Atlantic hurricane season ...

Hurricane Rita Hurricane Rita was the most intense tropical cyclone on record in the Gulf of Mexico, tying with Hurricane Milton in 2024 Atlantic hurricane season, 2024, as well as being the fourth-most intense Atlantic hurricane ever recorded. Part of the ...

Hurricane Ike Hurricane Ike () was a powerful tropical cyclone that swept through portions of the Greater Antilles and Northern America in September 2008, wreaking havoc on infrastructure and agriculture, particularly in Cuba and Texas. Ike took a sim ...

, Hurricane Laura and Hurricane Delta. Kirby explains how sediment deposition through the null point hypothesis leads to the creation of chenier. Sediment fines are suspended and reworked aerially offshore, leaving behind lag deposits of mainly bivalve and gastropod shells separated out from the finer substrate beneath. Waves and currents then heap these deposits to form chenier ridges throughout the tidal zone. They tend to force the deposits up the foreshore profile, but also along the foreshore.

Miranda, New Zealand

The chenier plain in Miranda in the

Firth of Thames The Firth of Thames () is a large bay located in the north of the North Island of New Zealand. It is the firth of the rivers Waihou and Piako, the former of which was formerly named the Thames River, and the town of Thames lies on its south ...

is one of the most significant Holocene coastal strand plains in the world and an important stopover point in the

godwit Godwits are a group of four large, long-billed, long-legged and strongly bird migration, migratory waders of the bird genus ''Limosa''. Their long bills allow them to probe deeply in the sand for aquatic worms and mollusca, molluscs. In their ...

flight path.

Essex, England

In Essex, ground-truthing data demonstrate that the radar profiles accurately delineate the subsurface stratigraphy and sedimentary structure of the cheniers. Interpretation of the radar stratigraphy taken from the radar reflection profiles allows various deposits to be identified. These have resulted from overwashing, overtopping, sedimentation across the whole of a seaward dipping beachface or berm ridge welding onto the upper beachface. Each chenier is characterised by a different spatial arrangement of these four basic depositional units.Neal, A.R.J., and K. Pye (2002) ''Structure and development of shell cheniers in Essex, southeast England, investigated using high frequency ground-penetrating radar.'' Marine Geology. v. 185, pp. 435-469.

Coastal plain of French Guiana, Suriname and Guyana

An extensive complex of

s and

swamps A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...

(''ritsen en zwampen'' in Suriname) was formed between the mouth of the Amazon River and the

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers approximately 1 million km2, with 65% of it in Venezuela and 35% in Colombia. It is the List of rivers by discharge, f ...

on the

coastal plain A coastal plain (also coastal plains, coastal lowland, coastal lowlands) is an area of flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and an upland area. Formation Coastal plains can f ...

of the

Guiana Shield The Guiana Shield (; ; ; ) is one of the three cratons of the South American Plate. It is a 1.7 billion-year-old Precambrian geological formation in northeast South America that forms a portion of the northern coast. The higher elevations on ...

. J.R.K. Daniel (1989) ''The chenier plain coastal system of Guyana'' Marine Geology. Volume 90, Issue 4, 30 December 1989, Pages 283-287 https://doi.org/10.1016/0025-3227(89)90130-8

References