Question

The given outcrop pattern on a flat topography represents: 

• A. Antiform with axial culmination
• B. Horizontal fold
• C. Plunging antiform
• D. Synform with axial depression

Hint:

On a map, straight parallel fold traces usually mean horizontal folds. Elliptical or eye-shaped closures always mean a plunging fold. Look at limb dips to decide antiform (convex up) vs synform (concave up).

Answer 1

The Correct Option is C

Step 1: Recall key fold geometry concepts.
- Antiform: A fold that is convex upwards (limbs dip away from the hinge). Whether it is an anticline or not depends on the facing direction of strata. - Synform: A fold that is concave upwards (limbs dip towards the hinge). - Horizontal fold: Fold axis is horizontal; map pattern is parallel bands, not closure. - Plunging fold: Fold axis is inclined (plunging into the ground); map pattern forms closures (elliptical or eye-shaped patterns) on a horizontal surface. - Axial culmination/depression: Refers to local highs or lows of the hinge line, not the closure itself.

Step 2: Interpret the figure.
- The map pattern shows elliptical eye-shaped closures, which indicate a plunging fold. - The fold axis is clearly drawn and is inclined toward both ends (not horizontal). - The convex-up shape with outward-dipping limbs indicates an antiform.

Step 3: Eliminate wrong options.
- (A) Antiform with axial culmination $\Rightarrow$ would not show elliptical closures but rather a culmination structure. Not correct. - (B) Horizontal fold $\Rightarrow$ would give parallel stripes in outcrop, not an eye pattern. Not correct. - (D) Synform with axial depression $\Rightarrow$ would be concave upwards, inconsistent with the given antiform geometry. Not correct.

Step 4: Correct interpretation.
Thus, the fold shown is an antiform with a plunging hinge line $\Rightarrow$ a plunging antiform.

Final Answer:
\[ \boxed{\text{Plunging antiform}} \]