Classification of Fold

Based on appearance in cross-section

1.Anticline:

The fold which is convex upwards and the limbs commonly dip away from the axial plane on either side of the axis, is called as anticline. In this case, the older rocks are occurred towards the centre of curvature of the fold. (Fig. 3.12)

2.Syncline

The fold which is concave upward and the Limbs commonly dip towards the axial plane on either side of the axis is called syncline. In this case, the younger rocks are occurred towards the centre of the curvature of the fold. See figure 3. 13

Based on position of axial plane

1.Symmetrical fold

The fold in which is axial plane divides the fold equally in two parts is called Symmetric fold. The fold may be anticline or syncline.

2.Asymmetrical fold

The fold in which is axial plane divides the fold unequally in two parts is called asymmetric fold. The fold may be anticline or syncline. (Fig. 3.14)

3.Overturned fold

The fold in which is axial plane is inclined and both the Limbs dip in the same direction, is called as overturned fold. The amount of death of the lens may or may not be same .It may be anticline or syncline. (Fig. 3.15).

4.Isoclinals fold

The group of hold in which is axial plane is essentially parallel in the Limbs are dipping in the same direction at equal angles are called as isoclinal fold. The axial plane may either be horizontal vertical or inclined. (Fig 3.16)

5.Recumbent fold:

The fold in which is axial plane is essentially horizontal and the limbs are dipping in the same directions horizontally is called as recumbent fold. (Fig. 3.17)

Based on mode of occurrence

1.Anticlinorium

The exceptionally large sized anticline fold with a number of small sized secondary fold is called as anticlinorium fold (Fig. 3.18)

2.Synclinorium

The exceptionally large sized syncline fold within number of small sized secondary fold is called synclinorium fold (figure 3. 19.)

3.Dome

The fold in which the Limbs are up folded in an arch like structure and dip away in all directions from a common Centre is called as dome fold (figure 3. 20.)

4.Basin

The fold in which the Limbs are down folded in a trough like structure and dip inform all directions to a common Centre is called as basin fold. (Fig 3.21)