‘Deccan Trap was hit by GHG effect 66m years ago’

AHMEDABAD: High temperatures due to Greenhouse Gas (GHG) effect and eventual torrential rainfall — it seems like the doomsday prophecy of today, but in fact it was something experienced 66 million years ago in the areas of Deccan Trap in modern-day Gujarat, Maharashtra and Madhya Pradesh.

The years in the Cretaceous period of geology where active volcanoes in the area spread the lava in the Deccan Trap experienced temperatures which were 13 degrees celsius higher than normal, making it unsustainable for the flora and fauna to survive. It was the period where dinosaurs and 80% of the living beings lost lives.

A recent paper ‘Triple oxygen isotopes in intertrappean fossil woods: Evidence of higher tropical rainfall during Deccan volcanism’ by Sangbaran Ghoshmaulik and others published in an Elsevier journal “Chemical Geology” has authors from IIT Kharagpur (IIT-K), Taipei-based Academia Sinica, University of Queensland, and SKB University.

The study analyzed oxygen isotopes retrieved from the fossilized trees in the Deccan Trap area to get a glimpse of the climate at that time.

Prof Anindya Sarkar from IIT-K, who was the lead researcher on the project, said that the Deccan Traps are one of the most voluminous basaltic volcanic lavas that erupted on Earth, covering over 5 lakh sq km of area in west-central Indian subcontinent.

Prof Mao Chang Liang from Academia Sinica said that the very high magnification images of several palm trees revealed cellular structures preserved just like modern trees. Ghoshmaulik, a doctoral student at IIT-K, said that it took about three years to develop the method through laser and nanoscale secondary mass spectrometry (NanoSIMS) to analyze the triple oxygen isotopes that gave the composition of the lake water. These trees experienced 1,800-1,900mm per year rainfall. “To put it in perspective, the modern annual rainfall over the large part of peninsular India is about 1,000-1,200 mm,” said co-author Sourendra Bhattacharya.


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