In structural geology, a syncline is a fold with younger layers closer to the center of the structure. 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).
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.
- 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.
- Saou, a commune in the Drôme department in southeastern France
- The Catlins, an area in the southeastern corner of the South Island of New Zealand
- Strathmore, Angus Syncline, Scotland
Syncline exposed in Sideling Hill roadcut
Road cut near Fort Davis, Texas showing a syncline
Syncline in the lower parking lot of Calico Ghost Town; the ductile folding is at the base and the brittle is above.
- Ridge-and-valley Appalachians –With good bird's eye photo of a range of the types
- Synclinorium. (2008). In Encyclopædia Britannica. Retrieved May 03, 2008, from Encyclopædia Britannica Online: http://www.britannica.com/EBchecked/topic/578375/synclinorium
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