In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an

anticline In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...

is the inverse of a syncline. A synclinorium (plural synclinoriums or synclinoria) is a large syncline with superimposed smaller folds. Synclines are typically a downward fold (synform), termed a synformal syncline (i.e. a trough), but synclines that point upwards can be found when strata have been overturned and folded (an antiformal syncline).

Characteristics

On a geologic map, synclines are recognized as a sequence of

rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...

layers Layer or layered may refer to: Arts, entertainment, and media * ''Layers'' (Kungs album) * ''Layers'' (Les McCann album) * ''Layers'' (Royce da 5'9" album) *"Layers", the title track of Royce da 5'9"'s sixth studio album *Layer, a female Maveric ...

, with the youngest at the fold's center or ''hinge'' and with a reverse sequence of the same rock layers on the opposite side of the hinge. If the fold pattern is circular or elongate, the structure is a basin. Folds typically form during crustal deformation as the result of compression that accompanies

orogenic Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...

mountain building.

Notable examples

Powder River Basin The Powder River Basin is a geologic structural basin in southeast Montana and northeast Wyoming, about east to west and north to south, known for its extensive coal reserves. The former hunting grounds of the Oglala Lakota, the area is very s ...

Wyoming Wyoming () is a U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho to the west, Utah to the south ...

, US *

Sideling Hill Sideling Hill, also Side Long Hill, is a long, steep, narrow mountain ridge in the Ridge-and-Valley (or Allegheny Mountains) physiographic province of the Appalachian Mountains, located in Washington County in western Maryland and adjacent West ...

roadcut along

Interstate 68 Interstate 68 (I-68) is a Interstate Highway in the US states of West Virginia and Maryland, connecting I-79 in Morgantown, West Virginia, to I-70 in Hancock, Maryland. I-68 is also Corridor E of the Appalachian Development Highway ...

in western

Maryland Maryland ( ) is a state in the Mid-Atlantic region of the United States. It shares borders with Virginia, West Virginia, and the District of Columbia to its south and west; Pennsylvania to its north; and Delaware and the Atlantic Ocean to ...

, US, where the

Rockwell Formation The Rockwell Formation is a late Devonian and early Mississippian mapped bedrock unit in West Virginia, Maryland, and Pennsylvania, in the United States. Description The Rockwell Formation was described at its type section at Rockwell Run in We ...

and overlying Purslane Sandstone are exposed * Forêt de Saou syncline in

Saou Saou () is a commune in the Drôme department in southeastern France. Population Syncline Saou is well known for its syncline. See also *Communes of the Drôme department The following is a list of the 363 communes of the Drôme depar ...

, France * The

Southland Syncline The Southland Syncline is a major geological structure located in the Southland Region of New Zealand's South Island. The syncline folds the Mesozoic greywackes of the Murihiku Terrane. The northern limb of the fold is steep to overturned, while ...

in the southeastern corner of the

South Island The South Island, also officially named , is the larger of the two major islands of New Zealand in surface area, the other being the smaller but more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman ...

of New Zealand, including

The Catlins The Catlins (sometimes referred to as The Catlins Coast) comprises an area in the southeastern corner of the South Island of New Zealand. The area lies between Balclutha and Invercargill, straddling the boundary between the Otago and Southla ...

and the

Hokonui Hills The Hokonui Hills, also known as ''The Hokonui Mountains'' or simply ''The Hokonui'', are a range of hills in central Southland, New Zealand. They rise to 600 metres above the surrounding Southland Plains, of which the hills mark a northern extre ...

* Strathmore Syncline, Scotland *

Wilpena Pound Wilpena Pound – also known by its Adnyamathanha language, Adnyamathanha name of Ikara, meaning "meeting place" – is a natural amphitheatre of mountains located north of Adelaide, South Australia, Australia in the heart of the Ikara-Flinders ...

Flinders Ranges The Flinders Ranges are the largest mountain range in South Australia, which starts about north of Adelaide. The ranges stretch for over from Port Pirie to Lake Callabonna. The Adnyamathanha people are the Aboriginal group who have inhabit ...

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

* Fort Valley, Shenandoah County, Virginia * The

Picuris Mountains The Picuris Mountains are a mountain range in northern New Mexico. They are considered a subrange of the Sangre de Cristo Mountains. Geography The mountains are located to the east of Dixon and surround Picuris Pueblo to the west, north, and ...

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe , LargestCity = Albuquerque , LargestMetro = Tiguex , OfficialLang = None , Languages = English, Spanish ( New Mexican), Navajo, Ker ...

, US, contain an example of an overturned syncline, the

Hondo Hondo may refer to: Places * Rio Hondo (disambiguation), the name of several locations, derived from the Spanish word for "deep" Canada * Hondo, Alberta, an unincorporated community United States * Hondo, New Mexico, an unincorporated co ...

Syncline.

Gallery

File:Sideling Hill cut MD1.jpg, Syncline exposed in

roadcut File:Provo Canyon syncline.jpg, Snow-dusted syncline in

Provo Canyon Provo Canyon is located in unincorporated Utah County and Wasatch County, Utah. Provo Canyon runs between Mount Timpanogos on the north and Mount Cascade on the south. The canyon extends from Orem on the west end to Heber City on the east. Provo ...

Utah Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...

File:Syncline.JPG, Road cut near

Fort Davis, Texas Fort Davis is an unincorporated community and census-designated place (CDP) in Jeff Davis County, Texas, United States. The population was 1,201 at the 2010 census, up from 1,050 at the 2000 census. It is the county seat of Jeff Davis County. His ...

showing a syncline File:Rainbow Basin.JPG,

Rainbow Basin Rainbow Basin is a geological formation in the Calico Peaks range, located approximately north of Barstow in the Mojave Desert in San Bernardino County, California. The Rainbow Basin has been designated a National Natural Landmark and is in th ...

Syncline in the

Barstow Formation The Barstow Formation is a series of limestones, conglomerates, sandstones, siltstones and shales exposed in the Mojave Desert near Barstow in San Bernardino County, California.Dibblee, T.W., Jr. (1967). Areal Geology of the Western Mojave De ...

near

Barstow, California Barstow is a city in San Bernardino County, California, in the Mojave Desert of Southern California. Located in the Inland Empire region of California, the population was 25,415 at the 2020 census. Barstow is an important crossroads for the In ...

File:SynclineCalico.JPG, Syncline in the lower parking lot of

Calico Ghost Town Calico is a ghost town and former mining town in San Bernardino County, California, United States. Located in the Calico Mountains of the Mojave Desert region of Southern California, it was founded in 1881 as a silver mining town, and was later c ...

; the ductile folding is at the base and the brittle is above. File:Roundtop Hill outcrop1.jpg, Synclinal fold in

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

Wills Creek Formation or

Bloomsburg Formation The Silurian Bloomsburg Formation is a mapped bedrock unit in Pennsylvania, New Jersey, New York and Maryland. It is named for the town of Bloomsburg, Pennsylvania in which it was first described. The Bloomsburg marked the first occurrence of red s ...

at Roundtop Hill (Maryland) File:Bear Valley east wall.jpg, East wall of

Bear Valley Strip Mine The Bear Valley Strip Mine is an abandoned coal strip mine located in Coal Township, Northumberland County, to the southwest of the town of Shamokin, Pennsylvania. It lies in the Western Middle Field of the Anthracite belt in the Ridge-and-Va ...

, near

Shamokin, Pennsylvania Shamokin (; Saponi Algonquian ''Schahamokink'', meaning "place of eels") ( Lenape Indian language: Shahëmokink) is a city in Northumberland County, Pennsylvania, United States. Surrounded by Coal Township at the western edge of the Anthracit ...

File:Upheaval Syncline campsite.jpg, Syncline in

Navajo Sandstone The Navajo Sandstone is a geological formation in the Glen Canyon Group that is spread across the U.S. states of southern Nevada, northern Arizona, northwest Colorado, and Utah as part of the Colorado Plateau province of the United States.Anonymo ...

Upheaval Dome Upheaval Dome is an enigmatic geological structure in San Juan County, Utah, United States, that has been variously interpreted as a meteorite impact structure or a salt dome. The structure lies southwest of the city of Moab, Utah, in the Islan ...

, Canyonlands National Park, Utah File:The Catlins.jpg, Satellite view of part of New Zealand's

, showing parallel folds running northwest–southeast File:Wilpena Pound - Aerial View.jpg,

, a synclinal basin in the

of South Australia

References

Structural geology {{Geology-stub