
In
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 layers, 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 mountain building.
Notable examples
*
Powder River Basin,
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 roadcut along
Interstate 68 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 and overlying
Purslane Sandstone are exposed
* Forêt de Saou syncline in
Saou, France
*
Southland Syncline 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 and the
Hokonui Hills
*
Strathmore Syncline, Scotland
*
Wilpena Pound,
Flinders Ranges,
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 Syncline in the
Picuris Mountains of
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 syncline, Nigeria
Gallery
File:Sideling Hill cut MD1.jpg, Syncline exposed in Sideling Hill roadcut
File:Provo Canyon syncline.jpg, Snow-dusted syncline in Provo Canyon, 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 showing a syncline
File:Rainbow Basin.JPG, Rainbow Basin Syncline in the Barstow Formation 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; 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 or Bloomsburg Formation 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, Utah
File:The Catlins.jpg, Satellite view of part of New Zealand's Southland Syncline, showing parallel folds running northwest–southeast
File:Wilpena Pound - Aerial View.jpg, Wilpena Pound, a synclinal basin in the Flinders Ranges of South Australia
See also
*
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 ...
*
Homocline
*
Monocline
*
Ridge-and-Valley Appalachians
*
Structural basin
References
Structural geology
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