A team of scientists from IIT Kharagpur and Academia Sinica, Taipei has indeed found evidence of very high annual rainfall during the catastrophic volcanism that formed the Deccan Traps in India about 66 million years back. They used a new technique — Nanoscale Secondary Ion Mass Spectrometry — to analyse three isotopes of oxygen (Oxygen-16,17, and 18) in fossil trees of the Cretaceous period and measure the isotopic composition of the lake water derived from rainfall.
The depleted values of the oxygen isotopes suggest a higher tropical rainfall (1,600 mm per year) in India during the terminal Cretaceous period. The increase in rainfall and its waning in the early Palaeocene closely follows change in palaeo-atmospheric (paleo carbon dioxide) suggesting a possible underlying link. Results were published in the Journal of Chemical Geology.
“The available records of the atmospheric carbon dioxide concentration and temperature over both land and ocean during the time of Deccan Trap eruption were analysed. Deccan trap lavas were erupting spewing huge amount of carbon dioxide thus increasing the then atmospheric carbon dioxide concentration to as high as 1,000 ppm (parts per million),” Prof. Anindya Sarkar from the Department of Geology and Geophysics at IIT Kharagpur and corresponding author of the paper said in a release.
