Global Geological And Climatic Events

Indian monsoon 25 million years ago resembled present day Australia’s


From UPSC perspective, the following things are important :

Prelims level : Drift of Indian plate from Gondwanaland

Mains level : History of Indian Monsoon

Using leaf fossils, researchers have found that the Indian monsoon 25 million years ago resembled present-day Australia’s.

Try this PYQ:

Q.Which one of the following is the appropriate reason for considering the Gondwana rocks as the most important rock systems of India?

(a) More than 90% of limestone reserves of India are found in them

(b) More than 90% of India’s coal reserves are found in them

(c) More than 90% of fertile black cotton soils are spread over them

(d) None of the reasons given above is appropriate in this context

India’s drift

  • About 180 million years ago, India separated from the ancient supercontinent Gondwana and took a long northward journey of about 9,000 km to join Eurasia.
  • During this journey, the subcontinent moved from the southern hemisphere, crossed the Equator to reach its current position in the northern hemisphere.
  • Due to these changing latitudes, it experienced different climatic conditions, and a new study has now tried to map these climatic variations using leaf fossils.

Clueless over the evolution of monsoon

  • The evolution of the monsoonal climate in India is still debatable and not fully understood.
  • Though recent data indicates that the monsoon system we experience now dates back to about 25 million years, it is still unclear how the climate was during its long voyage.

Indian research

  • The researchers analysed the morphological characters of fossil leaves collected from Deccan Volcanic Province, East Garo Hills of Meghalaya, Gurha mine in Rajasthan and Makum Coalfield in Assam.
  • The four fossil assemblages were found to be from four different geological ages.
  • It has been observed from across the globe that plant leaf morphological characters such as apex, base and shape are ecologically tuned with the prevailing climatic conditions.
  • The research applied this model to characterize the past monsoon from fossil leaves.

It’s finding

  • The results indicated that the fossil leaves from India were adapted to an Australian type of monsoon and not the current Indian monsoon system during its voyage.
  • The reconstructed temperature data show that the climate was warm (tropical to subtropical) at all the studied fossil sites with temperatures varying from 16.3–21.3 degrees C.
  • All the fossil sites experienced high rainfall, which varied from 191.6 cm to 232 cm.

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