structural geology Structural geology is the study of the three-dimensional distribution of rock units with respect to their deformational histories. The primary goal of structural geology is to use measurements of present-day rock geometries to uncover informati ...

, 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 (geology), fold that is an arch-like shape and has its oldest Bed (geology), beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex curve, c ...

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 Wale ...

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 ...

, 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 Orogeny () is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. This involv ...

as the result of compression that accompanies

orogenic Orogeny () is a mountain-building process that takes place at a convergent plate margin when plate motion compresses the margin. An or develops as the compressed plate crumples and is uplifted to form one or more mountain ranges. This involv ...

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 ...

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

, US *

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

roadcut along

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

in western

Maryland Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...

, 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 A commune is an alternative term for an intentional community. Com ...

, France *

Southland Syncline The Southland Syncline is a major geological structure located in the Southland, New Zealand, Southland Region of New Zealand's South Island. The syncline folds the Mesozoic Greywacke, greywackes of the Stratigraphy of New Zealand, Murihiku Terr ...

in the southeastern corner of the

South Island The South Island ( , 'the waters of Pounamu, Greenstone') is the largest of the three major islands of New Zealand by surface area, the others being the smaller but more populous North Island and Stewart Island. It is bordered to the north by ...

of New Zealand, including

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

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 ext ...

* Strathmore Syncline, Scotland *

Wilpena Pound Wilpena Pound ("Ikara" in the Adnyamathanha language) is a major natural amphitheatre of mountains located north of Adelaide, South Australia, Australia in the heart of the Ikara-Flinders Ranges National Park. Its fringe is accessible by a sea ...

Flinders Ranges The Flinders Ranges are the largest mountain ranges 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 inhab ...

South Australia South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...

* Fort Valley, Shenandoah County, Virginia *

Hondo Hondo 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 community * Hondo ...

Syncline in 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 New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

, an example of an overturned syncline *

Afikpo Ehugbo often referred to as Afikpo, is the second largest urban area in Ebonyi State, Nigeria. It is the headquarters of the Afikpo North Local Government Area. It is situated in the southern part of Ebonyi State and is bordered to the north by ...

syncline, Nigeria

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. P ...

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

File:Syncline.JPG, Road cut near

Fort Davis, Texas Fort Davis is an Unincorporated area, 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 ...

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 ...

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 Dese ...

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 United States census, 2020 census. Barstow is an impor ...

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 23.5 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 third and shortest period of t ...

Wills Creek Formation Wills Creek Formation is a mapped Silurian bedrock unit in Pennsylvania, Maryland, Virginia, and West Virginia. Description The Wills Creek is defined as a moderately well bedded greenish-gray shale containing local limestone and sandstone zon ...

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 ...

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

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

File:Upheaval Syncline campsite.jpg, Syncline in Navajo Sandstone, Upheaval Dome,

Canyonlands National Park Canyonlands National Park is a national park of the United States located in southeastern Utah near the town of Moab. The park preserves a colorful landscape eroded into numerous canyons, mesas, and buttes by the Colorado River, the Green Rive ...

, 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 {{struct-geology-stub