Anticlines

An anticline is a type of fold in layered rocks produced by compressional stress, forming an arching crest in which the beds dip away from a central hinge line. In an anticline, the oldest rock layers are typically found near the fold's core, with progressively younger layers toward the limbs.

Anticlines can be symmetric, with limbs dipping at similar angles, or asymmetrical, where one limb dips more steeply. If the hinge line plunges into the subsurface, the anticline becomes a plunging anticline, creating a tilted crest that may be traced over some distance.

Anticlines form during regional compression associated with mountain-building events, as well as by later tectonic processes and differential compaction. They may occur singly or as part of a train of folds produced by a single tectonic event.

Geologically, anticlines are important because their crest can trap hydrocarbons when an impermeable cap rock overlies a reservoir on the limbs. They are also useful in structural mapping and exploration, as their geometry helps reveal subsurface faults and rock relationships.

Examples occur worldwide in many orogens, including parts of the Appalachian mountains, the Zagros Mountains of Iran, and various foreland regions where compression has produced broad, long-wavelength anticlines.