Following figure represents an interference structure between two fold sets, $F_1$ and $F_2$
Which two of the following statements are correct?
A. Both $F_1$ - and $F_2$- hinge lines are parallel
B. Both $F_1$- and $F_2$ -folds are planar.
C. $F_1$-folds are non-planar but $F_2$- folds are planar
D. Both $F_1$- and $F_2$- folds are non-cylindrical
To solve this question, we need to analyze the given interference structure between two fold sets, $F_1$ and $F_2$, and determine which statements about these folds are correct.
Let's examine each statement:
- A. Both $F_1$ - and $F_2$- hinge lines are parallel:
The image shows that $F_1$ and $F_2$ fold hinges are aligned and appear to be parallel throughout. This statement is correct. - B. Both $F_1$- and $F_2$ -folds are planar:
A planar fold implies that the fold surface is flat. However, the given diagram suggests that the $F_1$ folds are curvilinear (non-planar). Thus, this statement is incorrect. - C. $F_1$-folds are non-planar but $F_2$-folds are planar:
As observed, $F_1$ folds are curvilinear (non-planar), while $F_2$ folds are planar (straight lines). This statement is correct. - D. Both $F_1$- and $F_2$- folds are non-cylindrical:
A non-cylindrical fold implies varying curvature. As $F_2$ folds are planar and cylindrical, this statement is incorrect.
By evaluating these statements, the two correct options are:
- Both $F_1$ and $F_2$ hinge lines are parallel.
- $F_1$-folds are non-planar but $F_2$-folds are planar.
Therefore, the correct answer is \(A \text{ and } C\).
Important Questions from Folds
The following figure shows the lower hemisphere, equal area plots of the poles to bedding surfaces. Which one of the following is the correct interpretation?
- The intersection of bedding surface with upright slaty cleavage surface occurs as horizontal lineation. Which one of the following is the most likely interpretation? The bedding surfaces are folded into
Figures A and B show two cross-sections of a folded sandstone bed.
Which one of the following is the correct interpretation of the Figs. A and B?
Match the outcrop patterns of folds with corresponding types.
Outcrop Patterns Fold A. 
P. Plunging antiform B. 
Q. Plunging synform C. 
R. Reclined D. 
S. Recumbent - Which one of the following is the correct angle between the hinge line and the strike line of the axial plane in a reclined fold?
