anticlinale

An anticlinale, or anticline, is a geologic fold in layered rocks produced by compressional forces. It presents as an arch-shaped structure in which the beds dip away from a central axis, or hinge line. In an anticline, the oldest rock layers are typically found near the fold’s core, with progressively younger rocks toward the limbs.

Geometrically, the hinge line traces the crest of the arch. Each limb tilts away from the hinge in opposite directions. Anticlines can be symmetric, with similar dips on both sides, or asymmetric, with one limb steeper than the other. They may also plunge when the hinge line itself inclines beneath the surface. Anticlines can occur as standalone features or as parts of larger fold systems, and erosion may remove overlying strata to leave a prominent topographic ridge.

Formation and significance: Anticlines form during crustal shortening and compression, such as during mountain-building events. They are important in petroleum geology because the arch can trap hydrocarbons migrating upward beneath an impermeable cap rock. The orientation and periodic repetition of anticlines influence regional geology, including erosion patterns and landscape development.

Relation to other structures: An anticline is the opposite of a syncline, a trough where the oldest rocks lie at the flanks and the core contains younger rocks. A monocline is a different, step-like curvature that lacks a true central arch.

Etymology: the term derives from Greek anti- “opposite” and klinē “slope,” referring to the opposite dips of the limbs.