Model Answer
0 min readIntroduction
Coal and lignite are crucial fossil fuels, representing significant energy resources for India. While bituminous coal dominates India’s energy mix, Tertiary coal deposits in Northeast India and lignite deposits in Tamil Nadu hold considerable economic importance. Tertiary coal, formed during the Paleogene and Neogene periods, differs in rank and characteristics from Gondwana coal. Lignite, a lower rank coal, is abundant in Tamil Nadu due to specific geological conditions. Understanding the geological settings and distribution patterns of these deposits is vital for resource management and sustainable energy planning.
Tertiary Coal Deposits in Northeast India
The Tertiary coal deposits of Northeast India are primarily found in Assam, Meghalaya, and Arunachal Pradesh. These deposits are significantly younger than the Gondwana coal fields found elsewhere in India, dating back to the Oligocene to Miocene epochs (approximately 34 to 5 million years ago).
Geological Setting
- Formation Environment: These coals formed in swampy deltaic environments associated with the foreland basin formed due to the Himalayan orogeny. Sedimentation was rapid, leading to the preservation of plant matter.
- Rock Types: The coal seams are interbedded with sandstones, shales, and conglomerates of the Barail and Kopili formations. These formations are part of the Assam-Arakan Basin.
- Structural Features: The region is characterized by thrust faulting and folding related to the Himalayan tectonic activity. These structures influence the distribution and thickness of the coal seams.
- Coal Rank: Tertiary coals are generally of lower rank than Gondwana coals, typically ranging from sub-bituminous to bituminous.
Distribution
- Assam: Major coalfields include Makum, Ledo, and Duliajan. The Makum coalfield is particularly significant, known for its high volatile matter content.
- Meghalaya: The Jaintia Hills and Garo Hills districts host substantial Tertiary coal reserves. These deposits are often associated with limestone formations. Significant open-cast mining occurs here.
- Arunachal Pradesh: Coal occurrences are found in the Changlang district, though reserves are relatively smaller compared to Assam and Meghalaya.
Lignite Deposits in Tamil Nadu
Tamil Nadu is the leading producer of lignite in India, accounting for over 90% of the country’s total lignite production. These deposits are of Miocene age (approximately 23 to 5 million years ago).
Geological Setting
- Formation Environment: Lignite formation occurred in shallow freshwater swamps and peat bogs within the fluvial and deltaic environments of the Cauvery Basin.
- Rock Types: Lignite seams are found within the sedimentary sequences of the Siwalik Group, specifically the Kalmadukku and Vilayur formations. These formations consist of sandstones, siltstones, and claystones.
- Structural Features: The region is relatively stable tectonically, with gentle dips and minor faulting. This has facilitated the preservation of the lignite seams.
- Coal Rank: Lignite is a low-rank coal, characterized by high moisture content and low calorific value.
Distribution
- Neyveli Lignite Field: This is the largest lignite field in India, located in the Cuddalore district. It is divided into Neyveli-I, Neyveli-II, and Neyveli-III mines.
- Biligiri Lignite Field: Situated in the Perambalur district, this field contributes significantly to Tamil Nadu’s lignite production.
- Other Occurrences: Smaller lignite occurrences are found in districts like Ariyalur and Thanjavur.
| Feature | Tertiary Coal (NE India) | Lignite (Tamil Nadu) |
|---|---|---|
| Age | Oligocene – Miocene | Miocene |
| Rank | Sub-bituminous to Bituminous | Lignite (Low Rank) |
| Geological Setting | Foreland basin, Assam-Arakan Basin | Cauvery Basin, Siwalik Group |
| Major Areas | Assam, Meghalaya, Arunachal Pradesh | Neyveli, Biligiri (Tamil Nadu) |
Conclusion
Both Tertiary coal deposits in Northeast India and lignite deposits in Tamil Nadu represent valuable energy resources, albeit with differing geological characteristics and economic implications. While the Tertiary coal is generally of higher rank, its extraction is often challenging due to complex geological structures and environmental concerns. Tamil Nadu’s lignite, though lower in rank, is readily accessible and plays a crucial role in the state’s power generation. Sustainable exploitation of these resources requires careful geological assessment, environmental management, and technological advancements.
Answer Length
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