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Indian volcano killed dinosaurs: Study

October 30, 2007 16:06 IST

What does Rajahmundry in Andhra Pradesh have to do with the mass extinction of dinosaurs? A lot, say scientists who delved deep into the most famous paleontological mystery on earth.

Research has shown that a series of monumental volcanic eruptions, which created gigantic Deccan Traps lava beds in India, may have wiped out dinosaurs 65 million years ago, dispelling notions that a meteor impact in the Gulf of Mexico did the same.

"It's the first time we can directly link the main phase of the Deccan Traps to the mass extinction," said Princeton University paleontologist Gerta Keller. The key phase of the Deccan eruptions spewed 80 percent of the lava, which spread out for miles and miles.

To explore deep into the mystery, Keller and her team will literally drill into the Rajahmundry Traps. The project is slated to take off  later this year.

According to volcanologist Vincent Courtillot from the Physique du Globe de Paris, the lava is said to have released 10 times more climate-altering gases into the atmosphere than the nearly concurrent Chicxulub meteor impact.

Keller's stunning evidence comes from microscopic marine fossils that are known to have evolved immediately after the highly mysterious mass extinction. The same telltale fossilized planktonic foraminifera were found in Rajahmundry near the Bay of Bengal, about 1,000 km from the centre of the Deccan Traps near Mumbai.

At Rajahmundry, the study says, there are two lava traps containing four layers of lava each. Between the traps are about nine meters of marine sediments. Those sediments just above the lower trap, which was the mammoth main phase, contain the incriminating micro-fossils.

Previous work had first zeroed down the Deccan eruption timing to within 800,000 years of the extinction event using paleomagnetic signatures of Earth's changing magnetic field frozen in minerals that crystallized from the cooling lava. Then radiometric dating of argon and potassium isotopes in minerals narrowed down it to 300,000 years of the 65-million-year-old Cretaceous-Tertiary boundary, now called the K-T boundary.

The micro-fossils are far more specific, however, because they demonstrate directly that the biggest phase of the eruption ended right when the aftermath of the mass extinction event began. That sort of clear-cut timing has been a lot tougher to pin down with Chicxulub-related sediments, which predate the mass extinction.

"Our results are consistent and mutually supportive with a number of new studies," said Keller. "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, Keller said.

Reports say Keller and her aide Thierry Adatte from the University of Neuchatel, Switzerland, will present the stunning findings on October 30 at the annual meeting of the Geological Society of America in Denver. They will also display a poster on the matter at the meet.