Model Answer
0 min readIntroduction
The Dharwar Supergroup represents one of the oldest and most important rock sequences in the Indian subcontinent, providing insights into the Archaean and Proterozoic geological evolution. Predominantly found in Karnataka, Andhra Pradesh, Telangana, and Tamil Nadu, it’s a vital source of information about early Earth processes and a significant host for various mineral deposits. The supergroup is characterized by a complex history of sedimentation, volcanism, and deformation, making its stratigraphic understanding crucial for resource exploration and geological research. Understanding its sequence is fundamental to deciphering the Precambrian geological history of India.
Stratigraphic Sequence of the Dharwar Supergroup
The Dharwar Supergroup is broadly divided into two main groups: the Older Metamorphic Group and the Younger Metamorphic Group, separated by an unconformity. These groups are further subdivided into formations based on lithological characteristics.
1. Older Metamorphic Group
This group represents the oldest part of the supergroup and is characterized by highly deformed and metamorphosed rocks. It is considered to be of Archaean age (older than 2.5 billion years).
- Bababudan Group: This is the basal unit, consisting of banded iron formations (BIFs), cherts, and ultramafic rocks. The BIFs are particularly significant economically.
- Chikmagalur Group: Predominantly composed of greywackes, shales, and banded hematite quartzites. It shows evidence of submarine volcanism.
- Kolar Group: Characterized by schists, gneisses, and iron formations. This group is famous for the Kolar Gold Fields.
2. Younger Metamorphic Group
This group overlies the Older Metamorphic Group with an unconformity and represents rocks of Proterozoic age (between 2.5 billion and 541 million years). It exhibits less intense deformation compared to the older group.
- Dharwar Group: Consists of shale, limestone, and conglomerate. It contains fossil evidence indicating the presence of early life forms.
- Gadag Group: Predominantly composed of sandstone, shale, and chert.
- Hutti Group: Known for its manganese deposits, this group consists of shale, chert, and banded manganese formations.
- Bennikera Group: Characterized by limestone, shale, and conglomerate.
3. Intrusive Rocks
Throughout the Dharwar Supergroup, various intrusive rocks are found, including granites, dolerites, and quartzites. These intrusions played a significant role in the metamorphism and deformation of the surrounding rocks.
Economic Importance of the Dharwar Supergroup
The Dharwar Supergroup is a treasure trove of mineral resources, contributing significantly to the Indian economy.
- Iron Ore: The BIFs of the Bababudan and Kolar Groups are major sources of iron ore. Karnataka is a leading producer of iron ore in India, largely due to these formations.
- Gold: The Kolar Gold Fields, within the Kolar Group, were historically one of the deepest gold mines in the world. Though currently closed, they represent a significant chapter in Indian mining history.
- Manganese: The Hutti Group is renowned for its high-grade manganese deposits, crucial for steel production.
- Chromite: Found associated with ultramafic rocks in the Bababudan Group.
- Limestone: The Dharwar and Bennikera Groups provide substantial limestone resources used in cement manufacturing.
- Copper: Minor occurrences of copper mineralization are found in various formations.
Geological Mapping & Exploration: The supergroup serves as a crucial area for geological mapping and mineral exploration, attracting both public and private sector investment.
| Group | Key Rock Types | Economic Minerals | Approximate Age |
|---|---|---|---|
| Older Metamorphic | BIFs, Greywackes, Schists, Gneisses | Iron Ore, Gold, Chromite | Archaean ( >2.5 Ga) |
| Younger Metamorphic | Shale, Limestone, Sandstone, Chert | Manganese, Limestone | Proterozoic (2.5 - 0.541 Ga) |
Conclusion
The Dharwar Supergroup stands as a testament to the ancient geological history of India, offering a window into the Earth’s early evolution. Its complex stratigraphic sequence, characterized by distinct formations and intrusive events, provides valuable insights for understanding Precambrian geology. Furthermore, its abundant mineral resources continue to play a vital role in the Indian economy. Continued research and sustainable exploration practices are crucial for maximizing the economic potential of this geologically significant region while preserving its geological heritage.
Answer Length
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