Dinosaurs killed by Indian volcanoes, not meteor: paleontologists

Volcanic eruptions in India, rather than a meteor impact in Mexico, could have been responsible for the extinction of the dinosaurs 65 million years ago, two American researchers say.

Princeton University paleontologist Gerta Keller and geologist Thierry Adatte from the University of Neuchatel, Switzerland, say they've foundtheend of theDeccan volcanic eruptions in India coincided with the aftermath of the mass extinction, known as the K-T, or Cretaceous-Tertiary, boundary.

The eruptions created the Deccan Traps lava beds in India, which cover almost 500,000 square kilometres.

In research presented Tuesday at the annual meeting of the Geological Society of America in Denver, the pair said fossils of marine life known to have evolved immediately after the dinosaurs died off can be found in layers of lava formed after the main eruption.

This finding, they argue, pinpoints the date of the eruptions to the same period as theextinction,supporting the theory that the dinosaurs were killed bygases spewed by the volcanoes.

The main period of eruptions isthought to have released 10 times more climate altering gases into the atmosphere than the Chicxulub meteor impact in the Gulf of Mexico, which happened during the same period and has also been blamed for the death of the dinosaurs.

"It's the first time we can directly link the main phase of the Deccan Traps to the mass extinction," Keller said in a release.

Previous research had narrowed the date of the eruptions to within 800,000 years of the extinction, based on the magnetic field of minerals in the lava. Dating of argon and potassium in the minerals later narrowed the gap to 300,000 years.

Keller and Adatte's research appears tofurther narrowed the timing, showing that the biggest phase of the eruptions ended as the aftermath of the death of the dinosaurs began.

The microscopic planktonic foraminifera, which evolved just after the extinction, were found in the top layers of the lava, whichformed after the main eruptions at Rajahmundry near the Bay of Bengal, about 1,000 kilometres from the centre of the traps near Mumbai.

The Rajahmundry traps consist of two lava traps containing four layers of lava each, with about nine metres of marine sediments between the layers. The sediments just above the lower trap, which was the main phase of the eruption, contain the incriminating microfossils.

"Our results are consistent and mutually supportive with a number of new studies … that reveal a very short time for the main Deccan eruptions at or near the K-T boundary and the massive carbon dioxide and sulphur dioxide output of each major eruption that dwarfs the output of Chicxulub," Keller said. "Our K-T age control combined with these results strongly points to Deccan volcanism as the likely leading contender in the K-T mass extinction."

The findings also help provide an answer as to why it took about 300,000 years for marine species to recover from the event that led to the extinction of the dinosaurs — thesecond phase of theDeccan Traps eruptions.

"The very last one was Early Danian, 280,000 years after the mass extinction, which coincides with the delayed recovery," Keller explained.

The researchers plan to explore the rocks directly beneath the main phase lava layers at Rajahmundry by drilling into the Rajahmundry Traps in December through January.

The study was funded by the National Science Foundation.