Question

Following are the statements regarding types of sandstone as per Pettijohn’s classification. Which is/are the CORRECT statement(s) out of the following?

• A. Arkose contains more than 25% feldspar.
• B. Greywacke contains more than 90% matrix.
• C. Litharenite contains more than 25% lithic fragment.
• D. Quartz arenite contains more than 95% quartz.

Hint:

Arkose = Feldspar-rich; Litharenite = Rock fragment-rich; Quartz arenite = Mature, quartz-dominant sandstone.

Answer 1

The Correct Option is A, C, D

Step 1: Pettijohn’s sandstone classification.
Sandstones are classified based on the relative proportions of quartz, feldspar, and lithic fragments (Q–F–L).
- Arkose: Feldspar >25%, quartz dominant.
- Greywacke: High matrix (15–25%), not 90%.
- Litharenite: Lithic fragments >25%.
- Quartz arenite: >95% quartz, well-sorted and mature.
Step 2: Conclusion.
Thus, correct statements are (A), (C), and (D).