The following types of folds have been recognised, on this basis

The following types of folds have been recognised, on this basis.

(i) Antiform:

Any upwardly convex structure is termed as an antiform. Here the age relationship between the upper and lower set of beds is of complex type.

(ii) Synform:

Any upwardly concave structure, i.e., flexure in the form of a trough is known as synform.

(iii) Anticline:

It is generally convex upwards where the limbs commonly slope away from the axial plane. In case of anticlines older beds occur towards the centre of curvature of the fold.

(iv) Syncline:

It is a fold which is concave upwards and the commonly dip towards the axial plane. Progressive younger beds are found towards the centre of curvature of the fold.

(vi) Synclinorium:

It is a large syncline with secondary folds of smaller size developed on it.

(vii) Anticlinal bend or Monocline:

It is due to local steepening of a bed, whereby there occurs a sudden increase in the dip of a bed, which is originally horizontal, to a near vertical position. Bat the original bedding remains as before.

(viii) Synclinal bend or structural terrace:

In case of a dipping bed, due to local flattening of the beds at a particular spot, the beds acquire horizontality and then again follow their original dip with­out any change in the direction of dip. These are also known as ‘structural bench’.