Types of Folds With Photos

An anticline fold is a type of fold that is convex upward, meaning that it looks like an "A" in cross-section. The oldest rocks are at the core of the fold, and the youngest rocks are on the flanks. Anticlines are often found in mountain ranges, where they are formed by the compression of the Earth's crust.

Anticlines can be symmetrical or asymmetrical. A symmetrical anticline is one in which the axial plane, which is the plane that divides the fold into two equal halves, is vertical. An asymmetrical anticline is one in which the axial plane is tilted.

Anticline is a fold that is convex up and has its oldest beds at its core. The term is not to be confused with antiform, which is a purely descriptive term for any fold that is convex up. Therefore if age relationships between various strata are unknown, the term antiform should be used.

A syncline is a fold with younger layers closer to the center of the structure. Synclines are typically a downward fold, termed a synformal syncline (i.e. a trough); but synclines that point upwards, or perched, can be found when strata have been overturned and folded (an antiformal syncline).

Monocline Fold

A monocline fold is a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently dipping sequence. Monoclines can be either symmetrical or asymmetrical, and the dip of the fold can range from a few degrees to nearly vertical.

local warping in horizontal strata. Rock beds lying at two level separated by steep inclined limbs. It is form by vertical movement and generally found fault below monocline. a step-like fold in rock strata consisting of a zone of steeper dip within an otherwise horizontal or gently-dipping sequence.

Chevron folds with flat-lying axial planes, Millook Haven, North Cornwall, UK

Chevron folds are a structural feature characterized by repeated well behaved folded beds with straight limbs and sharp hinges. Well developed, these folds develop repeated set of v-shaped beds. They develop in response to regional or local compressive stress. Inter-limb angles are generally 60 degrees or less. Chevron folding preferentially occurs when the bedding regularly alternates between contrasting competences. Chevron folds are typically found in mountain belts, where they can be used to infer the direction of compressive stress. They can also be found in sedimentary basins, where they can be used to map out the distribution of different rock types.

Recumbent fold in Oman

A recumbent fold is a fold in which the axial plane is essentially horizontal, meaning that the two limbs of the fold are parallel to the ground. Recumbent folds are often isoclinal, meaning that the limbs of the fold are also parallel to each other.

Recumbent folds can form in a variety of ways, but they are most commonly associated with mountain building events. When two tectonic plates collide, the crust can be thickened and compressed, causing the rocks to fold. Recumbent folds can also form in response to extensional forces, such as those that occur in rift valleys.

Isoclinal Fold

An isoclinal fold is a type of fold in which the limbs are parallel or nearly parallel to each other. This is in contrast to other types of folds, such as symmetrical folds, in which the limbs are at an angle to each other.

Isoclinal folds are formed by intense compressional forces. The forces are so strong that the limbs of the fold are forced to become parallel. Isoclinal folds are often found in mountain belts, where they have been formed by the collision of tectonic plates. Isoclinal folds are similar to symmetrical folds, but these folds both have the same angle and are parallel to each other. 'Iso' means 'the same' (symmetrical), and 'cline' means 'angle,' so this name literally means 'same angle.' So isoclinal folds are both symmetrical and aligned in a parallel fashion.

Plunging chevron folds

A fold whose axis plane is not horizontal (not Parallel to sea level). Direction of plunge - the direction in which the axis is inclined nose - indicate the direction of plunge. In anticline, plunge is directed towards nose and in syncline it is directed away from nose.

Desert of Mauritania. dome.

A dome and basin fold is a type of geological structure that consists of a central dome-shaped uplift surrounded by a basin-shaped depression. Dome and basin folds can be found in all types of tectonic settings, but they are particularly common in areas of compressional deformation, such as mountain belts.

Dome and basin folds can form in a variety of ways, but the most common mechanism is the interference of two or more sets of folds. When two sets of folds interfere, they can produce a variety of complex structures, including dome and basin folds. Dome: nonlinear, strata dip away from center in all directions, oldest strata in center. Basin: nonlinear, strata dip toward center in all directions, youngest strata in center.

Ptygmatic Fold

Slump Fold

Slump fold, California, USA