Question

The structure formed after the formation of host rock is called:

• A. geologic structure
• B. tectonic structure
• C. primary structure
• D. secondary structure

Hint:

Secondary structures = post-formation deformations like folds or faults.

Answer 1

The Correct Option is D

To identify the correct term for structures formed after host rock formation, we analyze geological structure classification.

1. Understanding Structure Formation:
Geological structures are categorized based on their timing relative to host rock formation.

2. Evaluating Each Option:
- Geologic structure: General term for all rock structures (too broad)
- Tectonic structure: Specifically formed by tectonic forces (not timing-dependent)
- Primary structure: Forms during rock formation (e.g., bedding planes in sedimentary rocks)
- Secondary structure: Correct answer - forms after host rock solidification

3. Characteristics of Secondary Structures:
- Develop through post-formation processes
- Includes folds, faults, and joints
- Results from tectonic stresses, weathering, or diagenesis
- Typically alters original rock fabric

4. Examples of Secondary Structures:
- Fault zones cutting across sedimentary layers
- Fracture systems in igneous intrusions
- Cleavage in metamorphic rocks

5. Why Other Options Are Incorrect:
- Primary structures form simultaneously with the rock
- Tectonic structures may be primary or secondary
- Geologic structure is a non-specific umbrella term

Conclusion:
The proper term for post-formation structures is secondary structure.

Final Answer:
The correct option is: secondary structure.