Model Answer
0 min readIntroduction
The Talchir Formation is the basal unit of the Gondwana Supergroup in India, representing the earliest phase of continental sedimentation following a period of widespread glaciation during the late Paleozoic era. It’s primarily found in the eastern and central parts of India, forming a significant part of the Gondwana coalfields. The formation is characterized by red beds, conglomerates, sandstones, and shales, indicating a transition from glacial to fluvial conditions. Understanding the Talchir Formation is crucial for deciphering the paleogeographic evolution of the Indian subcontinent and its relationship to the Permian-Triassic extinction event, one of the most severe biodiversity crises in Earth’s history.
Geological Setting and Lithology
The Talchir Formation occupies a crucial position in the stratigraphic column of India, marking the beginning of the Gondwana sequence. It overlies the archaean and proterozoic basement rocks and is unconformably overlain by the Barakar Formation. The formation is predominantly composed of coarse-grained clastic sediments deposited in a fluvial environment.
- Lithology: The Talchir Formation exhibits a diverse lithology, including:
- Conglomerates: Polymictic conglomerates containing clasts of various rock types, indicating high-energy depositional conditions.
- Sandstones: Arkose and feldspathic sandstones, suggesting rapid erosion of granitic source rocks.
- Shales: Red and purple shales, indicative of oxidizing conditions.
- Coal Seams: Though not as prominent as in the Barakar Formation, thin coal seams are present in some areas.
- Glacial Tillites: Evidence of glacial activity, particularly in the lower parts of the formation, suggesting a post-glacial depositional environment.
- Depositional Environment: The depositional environment is interpreted as a braided river system with alluvial fans and floodplains. The presence of coarse clastics suggests proximity to the source areas, while the red color of the sediments indicates oxidizing conditions.
Age and Correlation
Determining the precise age of the Talchir Formation has been a subject of debate. Traditionally, it was assigned to the Permian period. However, recent studies, including biostratigraphic and radiometric dating, suggest that it spans the Permian-Triassic boundary, ranging from late Permian to early Triassic (approximately 299 to 252 million years ago).
- Biostratigraphic Evidence: The presence of fossil plants like Glossopteris and Gangamopteris, along with fossil reptiles, supports a Permian-Triassic age.
- Radiometric Dating: Radiometric dating of associated volcanic rocks and detrital zircon U-Pb dating of sandstones have provided age constraints.
- Correlation: The Talchir Formation is correlated with similar sedimentary sequences in other Gondwana continents, such as Antarctica, Australia, and South Africa, indicating a shared geological history.
Geographical Distribution
The Talchir Formation is primarily found in eastern and central India, covering a vast area across several states.
| State | Major Outcrops |
|---|---|
| Odisha | Talcher, Angul, Dhenkanal |
| Jharkhand | Jharia, Raniganj, Bokaro |
| West Bengal | Raniganj, Asansol |
| Madhya Pradesh | Sohagpur, Pathakhera |
| Chhattisgarh | Korba, Hasdeo Valley |
Significance
The Talchir Formation holds significant geological and economic importance:
- Coal Formation: It serves as the base for the economically important Gondwana coalfields. While the Talchir itself doesn’t contain substantial coal seams, it provides the foundation for the overlying Barakar Formation, which is rich in coal deposits.
- Paleoclimatic Reconstruction: The lithological characteristics and fossil content of the Talchir Formation provide valuable insights into the paleoclimate and paleoenvironment of the region during the Permian-Triassic period.
- Permian-Triassic Extinction Event: Studying the Talchir Formation helps understand the impact of the Permian-Triassic extinction event on the Indian subcontinent.
- Sedimentary Basin Analysis: It provides crucial information for understanding the evolution of the Gondwana sedimentary basin.
Conclusion
The Talchir Formation represents a pivotal period in the geological history of India, marking the transition from glacial conditions to a warmer, fluvial environment. Its lithological diversity, stratigraphic position, and fossil content provide valuable insights into the paleogeography, paleoclimate, and biotic evolution of the region during the Permian-Triassic period. Further research, including detailed stratigraphic studies and radiometric dating, is crucial for refining our understanding of this important formation and its role in the evolution of the Indian subcontinent.
Answer Length
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