Model Answer
0 min readIntroduction
The Cretaceous-Paleogene (K-Pg) boundary, marking the transition between the Cretaceous and Paleogene periods approximately 66 million years ago, represents a pivotal moment in Earth’s history. This boundary is globally recognized by a thin layer of sediment enriched in iridium, an element rare in Earth’s crust but abundant in asteroids. This layer signifies a catastrophic extinction event that wiped out approximately 76% of plant and animal species, including non-avian dinosaurs. India provides crucial evidence related to this boundary, particularly through the Deccan Traps volcanism, which is increasingly recognized as a significant contributing factor to the extinction.
Understanding the K-Pg Boundary
The K-Pg boundary is characterized by several key geological markers. The most prominent is the iridium anomaly, first discovered in 1980 by Luis and Walter Alvarez at the Gubbio section in Italy. This iridium layer is found worldwide in sediments deposited at the K-Pg boundary. Other indicators include shocked quartz, tektites (glassy spherules formed from melted rock during impact), and soot, all suggesting a massive impact event. The prevailing theory attributes the extinction to an asteroid impact in the Yucatán Peninsula, Mexico, forming the Chicxulub crater.
Global Impact of the K-Pg Extinction
The impact triggered a cascade of environmental disasters. The initial impact would have caused widespread wildfires, tsunamis, and earthquakes. More significantly, vast amounts of dust and sulfur were ejected into the atmosphere, blocking sunlight and causing a prolonged period of global cooling, known as an impact winter. This disruption of photosynthesis led to the collapse of food chains, resulting in mass extinction. Marine ecosystems were also severely affected by the impact, with significant losses of plankton and marine reptiles.
Evidence from India: The Deccan Traps
India offers a unique perspective on the K-Pg boundary due to the presence of the Deccan Traps, one of the largest volcanic features on Earth. These massive flood basalts were erupted over a period of approximately 750,000 years around the K-Pg boundary. The Deccan Traps are composed of layered basalt flows covering a vast area of western India.
The Role of Deccan Traps Volcanism
For a long time, the asteroid impact was considered the sole cause of the K-Pg extinction. However, recent research suggests that the Deccan Traps volcanism played a significant, and potentially synergistic, role. The eruptions released massive amounts of greenhouse gases (CO2, SO2) and aerosols into the atmosphere, causing both short-term cooling and long-term warming. This climatic instability, coupled with ocean acidification, may have already stressed ecosystems before the asteroid impact, making them more vulnerable to extinction.
Geological Evidence in India
- Rajmahal Hills, Jharkhand: These hills contain K-Pg boundary sediments with elevated iridium levels, though often less pronounced than at the Gubbio section.
- Western Ghats Basalt Province: The Deccan Traps themselves provide evidence of massive volcanic activity coinciding with the K-Pg boundary. Detailed dating of the basalt flows reveals that a significant portion of the eruptions occurred around the time of the impact.
- Krishna-Godavari Basin: Sedimentary records in this basin show evidence of both the impact ejecta layer and the effects of Deccan Traps volcanism, providing a combined record of the events.
Recent Research & Debate
Recent high-precision dating of the Deccan Traps using Argon-Argon dating techniques has shown that the most intense phase of volcanism occurred *immediately* after the Chicxulub impact. This suggests that the impact may have triggered or exacerbated the volcanic activity, creating a “double whammy” effect. However, the exact relationship between the impact and the volcanism remains a subject of ongoing research and debate.
| Event | Timing (Millions of Years Ago) | Evidence in India |
|---|---|---|
| Chicxulub Impact | ~66.04 Ma | Iridium anomaly in Rajmahal Hills, Krishna-Godavari Basin |
| Deccan Traps Volcanism | ~66.0-65.5 Ma | Extensive basalt flows in Western Ghats, geochemical signatures in K-Pg boundary sediments |
Conclusion
The K-Pg boundary represents a dramatic turning point in Earth’s history, marked by a catastrophic extinction event. While the Chicxulub impact is widely accepted as a major trigger, the role of the Deccan Traps volcanism in India is increasingly recognized as a crucial contributing factor. The interplay between these two events likely created a complex and devastating environmental scenario that led to the demise of the dinosaurs and reshaped the course of life on Earth. Further research, particularly focusing on high-resolution dating and geochemical analysis, is essential to fully understand the dynamics of this pivotal period.
Answer Length
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