Note the man standing in front of the formation, for scale. In structural historical geology reed wicander pdf, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core.
The progressing age of the rock strata towards the core and uplifted center, are the trademark indications for evidence of anticlines on a geologic map. These formations occur because anticlinal ridges typically develop above thrust faults during crustal deformations. An antiform can be used to describe any fold that is convex up. It is the relative ages of the rock strata that distinguish anticlines from antiforms.
The hinge of an anticline refers to the location where the curvature is greatest, also called the crest. The hinge is also the highest point on a stratum along the top of the fold. The culmination also refers to the highest point along any geologic structure. The axial surface is an imaginary plane connecting the hinge of each layer of rock stratum through the cross section of an anticline. If the axial surface is vertical and the angles on each side of the fold are equivalent, then the anticline is symmetrical. If the axial plane is tilted or offset, then the anticline is asymmetrical. An anticline that is cylindrical has a well-defined axial surface, whereas non-cylindrical anticlines are too complex to have a single axial plane.
An overturned anticline is an asymmetrical anticline with a limb that has been tilted beyond perpendicular, so that the beds in that limb have basically flipped over and may dip in the same direction on both sides of the axial plane. Oldest beds are in the center and youngest on the outside. The axial plane intersects the center angle of bend. The hinge line follows the line of greatest bend, where the axial plane intersects the outside of the fold. Folds in which the limbs dip toward the hinge and display a more U-like shape are called synclines.