Question:
Which of the following materials is/are used for estimation of hydrocarbon source rock maturation based on color?
Which of the following materials is/are used for estimation of hydrocarbon source rock maturation based on color?
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- CAI (Conodont Color Alteration Index) → Thermal maturity.
- SCI (Spore Color Index) → Hydrocarbon source rock maturation.
- Illite and Zircon are not used for color-based maturity evaluation.
- SCI (Spore Color Index) → Hydrocarbon source rock maturation.
- Illite and Zircon are not used for color-based maturity evaluation.
Updated On: Aug 21, 2025
- Conodont
- Illite
- Spore
- Zircon
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The Correct Option is A, C
Solution and Explanation
Step 1: Concept of color-based maturity indicators.
The maturity of organic-rich rocks can be evaluated by the color alteration of certain organic microfossils and palynomorphs. With increasing thermal maturity, their color changes systematically, making them effective maturity indicators.
Step 2: Conodont Color Alteration Index (CAI).
- Conodonts are microfossils whose color darkens with increasing burial and temperature.
- The Conodont Color Alteration Index (CAI) is widely used to estimate paleotemperatures and thermal maturity of source rocks.
- Hence, (A) Conodont is correct.
Step 3: Spore Color Index (SCI).
- Spores and pollen grains also show progressive color darkening with thermal maturity.
- The Spore Color Index (SCI) is another standard method for estimating hydrocarbon source rock maturation.
- Hence, (C) Spore is correct.
Step 4: Incorrect options.
- (B) Illite: Used in illite crystallinity studies for metamorphic grade, not for color-based maturity.
- (D) Zircon: Used for U–Pb geochronology and fission-track dating, not color maturation.
Step 5: Final Answer.
Thus, the correct indicators are: \[ \boxed{\text{Conodont (A) and Spore (C)}} \]
The maturity of organic-rich rocks can be evaluated by the color alteration of certain organic microfossils and palynomorphs. With increasing thermal maturity, their color changes systematically, making them effective maturity indicators.
Step 2: Conodont Color Alteration Index (CAI).
- Conodonts are microfossils whose color darkens with increasing burial and temperature.
- The Conodont Color Alteration Index (CAI) is widely used to estimate paleotemperatures and thermal maturity of source rocks.
- Hence, (A) Conodont is correct.
Step 3: Spore Color Index (SCI).
- Spores and pollen grains also show progressive color darkening with thermal maturity.
- The Spore Color Index (SCI) is another standard method for estimating hydrocarbon source rock maturation.
- Hence, (C) Spore is correct.
Step 4: Incorrect options.
- (B) Illite: Used in illite crystallinity studies for metamorphic grade, not for color-based maturity.
- (D) Zircon: Used for U–Pb geochronology and fission-track dating, not color maturation.
Step 5: Final Answer.
Thus, the correct indicators are: \[ \boxed{\text{Conodont (A) and Spore (C)}} \]
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