Lacassine national wildlife refuge Louisiana

A chenier or chénier is a sandy or shelly

beach ridge A beach ridge is a wave-swept or wave-deposited ridge running parallel to a shoreline. It is commonly composed of sand as well as sediment worked from underlying beach material. The movement of sediment by wave action is called '' littoral tr ...

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 swales. A strand plain differs from a barrier island in that it lacks ei ...

, called a “chenier plain,” consisting of cheniers separated by intervening mud-flat deposits with marsh and swamp vegetation. Cheniers are typically 1 to 6 m high, tens of km long, hundreds of metres wide, and often wooded. Chenier plains can be tens of km 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 French word for wood, “chêne,” meaning oak, which grows on 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 f ...

of the

Colorado River Delta The Colorado River Delta is the region where the Colorado River flows 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 northwesternmost Mexico. The d ...

in northeastern

Baja California Baja California (; 'Lower California'), officially the Free and Sovereign State of Baja California ( es, Estado Libre y Soberano de Baja California), is a state in Mexico. It is the northernmost and westernmost of the 32 federal entities of Me ...

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Gua ...

.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, adjoining the city of Port Arthur. The lake is formed by the confluence of the Neches and Sabine Rivers and connec ...

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 Cameron Parish (french: Paroisse de Cameron) is a parish in the southwest corner of the U.S. state of Louisiana. As of the 2020 census, the population was 5,617. The parish seat is Cameron. Although it is the largest parish by area in Louisia ...

, Pecan Island in Vermilion Parish and the former settlement of Cheniere Caminada adjacent to Grand Isle, south of

New Orleans New Orleans ( , ,New Orleans

. 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 tropical cyclones in U.S. history, killing at least 416 people in its devastation of the southwestern Louisiana coast in 1957. Along with Hurricane Alex in 2010, it was also the strongest June hur ...

Hurricane Rita Hurricane Rita was the most intense tropical cyclone on record in the Gulf of Mexico and the fourth-most intense Atlantic hurricane ever recorded. Part of the record-breaking 2005 Atlantic hurricane season, which included three of the top ten ...

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 Hurricane Laura was a deadly and destructive Category 4 hurricane that is tied with the 1856 Last Island hurricane and 2021's Hurricane Ida as the strongest hurricane on record to make landfall in the U.S. state of Louisiana, as measure ...

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 ( mi, Tikapa Moana-o-Hauraki) 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 ...

is one of the most significant Holocene coastal strand plains in the world and an important stopover point in the godwit 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 The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of ...

and the

Orinoco The Orinoco () is one of the longest rivers in South America at . Its drainage basin, sometimes known as the Orinoquia, covers , with 76.3 percent of it in Venezuela and the remainder in Colombia. It is the fourth largest river in the wo ...

on the

coastal plain A coastal plain is flat, low-lying land adjacent to a sea coast. A fall line commonly marks the border between a coastal plain and a piedmont area. Some of the largest coastal plains are in Alaska and the southeastern United States. The Gulf Co ...

of the

Guiana Shield The Guiana Shield (french: Plateau des Guyanes, Bouclier guyanais; nl, Hoogland van Guyana, Guianaschild; pt, Planalto das Guianas, Escudo das Guianas; es, Escudo guayanés) is one of the three cratons of the South American Plate. It is a 1 ...

. 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