In structural geology, a syncline is a fold with younger layers closer to the center of the structure, whereas an anticline 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, US
- Sideling Hill roadcut along Interstate 68 in western Maryland, US, where the Rockwell Formation and overlying Purslane Sandstone are exposed
- Forêt de Saou syncline in Saou, France
- The Southland Syncline in the southeastern corner of the South Island of New Zealand, including The Catlins and the Hokonui Hills
- Strathmore Syncline, Scotland
- Wilpena Pound, Flinders Ranges, South Australia
- Fort Valley, Shenandoah County, Virginia
- Hondo Syncline in the Picuris Mountains of New Mexico, an example of an overturned syncline.
Gallery
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Syncline exposed in Sideling Hill roadcut
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Snow-dusted syncline in Provo Canyon, Utah
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Road cut near Fort Davis, Texas showing a syncline
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Rainbow Basin Syncline in the Barstow Formation near Barstow, California
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Syncline in the lower parking lot of Calico Ghost Town; the ductile folding is at the base and the brittle is above.
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Synclinal fold in Silurian Wills Creek Formation or Bloomsburg Formation at Roundtop Hill (Maryland)
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East wall of Bear Valley Strip Mine, near Shamokin, Pennsylvania
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Syncline in Navajo Sandstone, Upheaval Dome, Canyonlands National Park, Utah
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Satellite view of part of New Zealand's Southland Syncline, showing parallel folds running northwest–southeast
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Wilpena Pound, a synclinal basin in the Flinders Ranges of South Australia
See also
References
- Synclinorium. (2008). In Encyclopædia Britannica. Retrieved May 03, 2008, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/578375/synclinorium
- Bauer, Paul W.; Williams, Michael L. (August 1989). "Stratigraphic nomenclature ol proterozoic rocks, northern New Mexico-revisions, redefinitions, and formalization" (PDF). New Mexico Geology. 11 (3): 45–52. doi:10.58799/NMG-v11n3.45. Retrieved 15 April 2020.
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