California Syncline

Fitzgerald Marine Preserve, San Mateo County, CA

A syncline is a fold with younger layers closer to the center of the structure.  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).

Syncline in the lower parking lot of Calico Ghost Town; the ductile folding is at the base and the brittle is above. Calico Ghost Town near Barstow, California.