Question

In the fold profile section shown in the figure, 1 and 3 are the oldest and the youngest stratigraphic units, respectively. Which one of the following fold descriptions CORRECTLY matches the asymmetric fold shown in the given figure?

• A. Antiform facing east
• B. Synform facing east
• C. Antiform facing west
• D. Synform facing west

Hint:

- \textbf{Antiform:} Convex upward fold.
- \textbf{Synform:} Concave upward fold.
- Facing depends on younging direction: if beds young toward west → west-facing; if beds young toward east → east-facing.

Answer 1

The Correct Option is C

Step 1: Determining fold geometry (antiform vs. synform).
From the figure, the fold profile is clearly convex upwards, i.e., limbs dip away from the hinge zone. This is the definition of an antiform.
Step 2: Determining fold facing direction.
The sequence is given: unit 1 = oldest, unit 3 = youngest. Observing the diagram, the axial trace and younging direction indicate that the fold is overturned toward the west. The younging (from 1 to 3) goes westward in the fold profile. Thus, the fold is west-facing.
Step 3: Combine results.
- Form: Antiform (convex upward)
- Facing: West
Hence, the correct description is: \[ \boxed{\text{Antiform facing west (Option C)}} \]