Question

Which one of the following statements is correct for Class 1B (Parallel) folds?

• A. Orthogonal thickness at hinge>that at limb
• B. Axial planar thickness at hinge = that at limb
• C. Dip isogons are parallel
• D. Dip isogons are convergent

Hint:

In structural geology, Class 1B (parallel) folds exhibit parallel dip isogons and symmetrical layering.

Answer 1

The Correct Option is C

Step 1: Understanding the question.
Class 1B folds, also known as parallel folds, are characterized by parallel isogons and symmetrical structures. The question asks about their specific structural features.
Step 2: Analyzing the options.
(A) Orthogonal thickness at hinge>that at limb: This is not true for Class 1B folds.
(B) Axial planar thickness at hinge = that at limb: This is not typical of Class 1B folds.
(C) Dip isogons are parallel: Correct — In Class 1B folds, the dip isogons (lines of equal dip) are parallel.
(D) Dip isogons are convergent: This is not true for parallel folds.
Step 3: Conclusion.
The correct answer is (C) Dip isogons are parallel, as this is a defining characteristic of Class 1B folds.