Question

Attitudes of the two limbs of a non-plunging kink fold shown below are 045°, 20°SE and 045°, 40°NW. The dip amount (in degrees) of the axial plane of the kink fold is ............ (answer in one decimal place). 

 

Hint:

For a kink fold, the dip of the axial plane can be found by averaging the dip amounts of the two limbs.

Answer 1

Correct Answer: 70 - 90

The fold is non-plunging, and both limbs have the same strike (045°), so the problem reduces to a 2-D cross-section perpendicular to strike.

Limb dips:

Limb 1: 40° NW

Limb 2: 20° SE

In cross-section, the angle between the two limb planes is:
\[180^\circ - (40^\circ + 20^\circ) = 120^\circ\]

The axial plane bisects this interlimb angle:
\[\frac{120^\circ}{2} = 60^\circ\]

Measured from either limb:

From the 20° limb: \( 20^\circ + 60^\circ = 80^\circ \)