<P> 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, 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). </P> <P> 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 . </P> <Ul> <Li> Powder River Basin, Wyoming, US </Li> <Li> Sideling Hill roadcut along Interstate 68 in western Maryland, US, where the Rockwell Formation and overlying Purslane Sandstone are exposed . </Li> <Li> Saou, a commune in the Drôme department in southeastern France </Li> <Li> The Catlins, an area in the southeastern corner of the South Island of New Zealand </Li> <Li> Strathmore, Angus Syncline, Scotland </Li> </Ul>

Where are the oldest rocks found in a syncline