anticlinal

An anticlinal, or anticline when used as a noun, is a type of geological fold formed by compressional forces in rock layers. It is defined by an arch-shaped structure in which the beds dip away from a central hinge line or axis, with the oldest strata typically located at the core of the fold. In map view, an anticline often appears as a rounded crest bounded by outward-dipping limbs.

Anticlines arise during tectonic deformation associated with mountain building and other compression events. The hinge line may be horizontal or inclined, producing symmetric or plunging anticlines. The limbs slope away from the axis, and a plunging anticline curves downward so its crest disappears beneath the surface along its plunge direction.

Compared with synclines, where beds dip toward the fold axis and the youngest rocks are at the core, anticlines expose older rocks in the center. Recognition relies on lithology and fossil content to determine the organization of layers and their relative ages along the limbs and core.

Economically, anticlines can form structural traps that hold hydrocarbons or groundwater when impermeable layers cap the reservoir rock. They are a key feature in petroleum geology and exploration, helping guide drilling and field mapping. Examples can be found in many orogenic belts worldwide, where repeated folding produces complex anticlines.