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 Southland Syncline in the southeastern corner of the South Island of New Zealand, including The Catlins and the Hokonui Hills
- Strathmore, Angus Syncline, Scotland
- Lake Superior lies within the core of a large syncline that was preferentially eroded by ice during the Wisconsin glaciation
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.
Satellite view of part of New Zealand's Southland Syncline, showing parallel folds running northwest-southeast
- 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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