Which ONE of the following rocks shows the highest reading in the natural gamma ray log?
Show Hint
- Dolomite
- Anhydrite
- Oil Shale
- Limestone
The Correct Option is C
Solution and Explanation
Step 1: Recall gamma ray logging principle.
Natural gamma ray logs measure the natural radioactivity of formations, primarily caused by uranium, thorium, and potassium-bearing minerals. Step 2: Compare rocks.
- Dolomite → clean carbonate, very low gamma. - Anhydrite → evaporite mineral, almost no gamma. - Limestone → clean carbonate, low gamma. - Oil Shale → contains abundant clays and organic matter, with high concentrations of radioactive elements → highest gamma response. Step 3: Conclusion.
Among the given options, oil shale exhibits the highest natural gamma ray reading. Final Answer: \[ \boxed{\text{Oil Shale}} \]
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