Geometry and elements of

fold

The bending of rock strata of plastic nature due to compressional forces acting horizontally towards a common point or plane from opposite directions is known as folding.

INTRODUCTION

It results in the crumbling of strata , resulting in a wavy formation on the surface of the earth , which are known as folds.

Folds are described by their form & orientation.

CONTINUE...

The stretch of the rock beds lying between any crest and any of the adjacent troughs on either sides is known as the limb of the fold.

The limb may be then redefined as the fold segment between a hinge line and the adjacent inflection line.

1.LIMBS

A point can be found where curvature is maximum is called hinge point.

When rocks occur in a sequence & their all hinge points are joined together , they make a line , called the hinge line.

2.HINGE

An axial plane is that imaginary plane that passes through all the points of maximum curvature in a folded sequence.

It may be vertical , inclined or horizontal in nature.

3.AXIAL PLANE

A line drawn parallel to the hinge line of a fold.

A precise definition is the line representing the intersection of the axial plane of a fold with any bed of the fold.

4.AXIS OF A FOLD

The angle of inclination of the fold axis with the horizontal as measured in a vertical plane is termed the plunge of the fold.

In other words , plunge is the angle which this line makes with a horizontal plane.

5.PLUNGE OF A FOLD

Crest-Highest points in an uparchedfold.

Trough-Lowest point in a downarchedfold.

Inflection point-A point on a fold at which the fold changes from syncline to anticline or vice versa.

6.CREST,TROUGH & INFLECTION POINT

Engineering & general geology-ParbinSingh.

A textbook of geology-G.B.Mahabatra

https://en.wikipedia.org/wiki/File:Flank_%26_hinge.PNG

https://en.wikipedia.org/wiki/File:Agiospavlos_DM_2004_IMG002_Felsenformation.JPG

REFERNCE

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