Question

A limestone contains lime mud and around 25% allochems, which are separated from each other. The name of the rock as per Dunham’s classification is

• A. mudstone
• B. wackestone
• C. packstone
• D. grainstone

Hint:

In Dunham’s scheme: increasing allochems → mudstone → wackestone → packstone → grainstone.

Answer 1

The Correct Option is B

Step 1: Understanding Dunham’s classification.
Dunham (1962) classified limestones based on the proportion of allochems (grains) and micrite (lime mud).
- Mudstone: >90% micrite, very few grains.
- Wackestone: Mud-supported rock with >10% grains (allochems not touching).
- Packstone: Grain-supported rock with mud matrix present.
- Grainstone: Grain-supported, no mud.
Step 2: Application.
Since the rock contains lime mud and about 25% allochems (grains not touching each other), it fits the definition of a wackestone.
Step 3: Conclusion.
Hence, the limestone is classified as wackestone.