Model Answer
0 min readIntroduction
The transition from the Paleogene to the Neogene represents a crucial period in Earth’s history, marked by significant climatic shifts, tectonic rearrangements, and evolutionary changes. In the Indian context, this transition (roughly 23 million years ago) witnessed the culmination of the India-Asia collision, leading to profound alterations in the subcontinent’s paleogeography. Prior to this, India was undergoing a period of marine transgression and regression, coupled with the formation of extensive sedimentary basins. Understanding the paleogeography during this transition is vital for reconstructing the evolution of the Himalayan orogen and the surrounding regions, and for interpreting the distribution of resources like hydrocarbons.
Early Paleogene (Paleocene-Eocene): Initial Collision & Marine Environments
The Paleocene-Eocene epochs (66-56 million years ago) saw the initial stages of the India-Asia collision. While not a hard collision, the slowing of the Indian plate led to the development of foreland basins. Marine conditions prevailed across much of western India, with the deposition of thick sequences of carbonates and shales. The Kutch Basin and Cambay Basin were prominent features, receiving sediments from the weathering of the Deccan Traps and the nascent Himalayas. Fossil evidence from this period indicates a warm, tropical climate with diverse marine fauna.
Mid-Paleogene (Oligocene): Intensifying Collision & Basin Development
The Oligocene epoch (34-23.03 million years ago) witnessed an intensification of the India-Asia collision. This resulted in increased uplift in the Himalayan region and the development of extensive foreland basins, including the Indo-Gangetic Plain. Sedimentation rates increased significantly as the Himalayas began to erode. The Kutch and Cambay basins continued to receive sediments, but the nature of deposition shifted towards more clastic sediments (sandstones and shales) due to increased erosion. The first signs of significant fluvial systems draining from the Himalayas appeared.
Paleogene-Neogene Boundary (Aquitanian-Burdigalian): A Turning Point
The transition at the Paleogene-Neogene boundary (around 23 million years ago) was a pivotal moment. The collision entered a more vigorous phase, leading to rapid uplift of the Himalayas and the formation of the Siwalik Group – a thick sequence of molasse deposits. This period saw a significant change in the drainage pattern of the Indian subcontinent. The Tethys Sea retreated, and the Indo-Gangetic Plain began to take shape as a vast alluvial fan. The formation of the Bengal Basin also commenced, receiving sediments from the Ganges-Brahmaputra river system.
Neogene (Miocene-Pliocene): Himalayan Orogeny & Basin Maturation
The Miocene and Pliocene epochs (23.03-2.58 million years ago) were characterized by continued Himalayan orogeny and the maturation of the sedimentary basins. The Siwalik Group accumulated rapidly, preserving a rich record of mammalian fossils, including early hominids. The Indo-Gangetic Plain expanded further, becoming a major depositional center. The Bengal Basin continued to receive massive sediment input, leading to its progradation. The climate began to cool and become more seasonal, influencing the distribution of flora and fauna. The development of the Thar Desert also began during this period, influenced by changes in monsoon patterns.
Key Paleogeographical Features during the Transition:
- Himalayan Orogeny: Continued uplift and erosion, leading to sediment supply to foreland basins.
- Foreland Basin Development: Expansion of the Indo-Gangetic Plain and Bengal Basin.
- Tethys Sea Regression: Retreat of the Tethys Sea and the formation of land connections.
- Drainage Pattern Evolution: Establishment of the major river systems of the Indian subcontinent (Indus, Ganges-Brahmaputra).
- Sedimentary Basin Fill: Accumulation of thick sedimentary sequences in the Kutch, Cambay, and Siwalik basins.
| Period | Paleogeographical Features | Dominant Sedimentary Deposits |
|---|---|---|
| Paleocene-Eocene | Initial India-Asia collision, widespread marine conditions | Carbonates, shales |
| Oligocene | Intensifying collision, foreland basin development | Clastic sediments (sandstones, shales) |
| Aquitanian-Burdigalian | Vigorous collision, Siwalik Group formation, Tethys Sea retreat | Molasse deposits (gravel, sand, silt) |
| Miocene-Pliocene | Continued orogeny, basin maturation, climate cooling | Alluvial sediments, evaporites |
Conclusion
The Paleogene-Neogene transition in India was a period of dramatic paleogeographical change driven by the India-Asia collision. This transition resulted in the formation of the Himalayas, the development of extensive sedimentary basins, and the establishment of the modern drainage patterns of the subcontinent. Understanding these changes is crucial for interpreting the geological history of India and for assessing its resource potential. Further research, including detailed stratigraphic studies and paleomagnetic analyses, will continue to refine our understanding of this critical period in Earth’s history.
Answer Length
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