Sunday, November 13, 2011

Oil hunt discovers Deccan dino destroyer

http://www.telegraphindia.com/1111113/jsp/frontpage/story_14743843.jsp
Oil hunt discovers Deccan dino destroyer

New Delhi, Nov. 12: India's search for oil has revealed a geological club sandwich of fossils that scientists say is the first direct evidence for the theory that volcanic eruptions in western India caused the mass extinction that wiped out the dinosaurs.

Scientists from India, Switzerland and the US who studied tiny fossils sandwiched between volcanic layers beneath the Krishna-Godavari basin and the Bay of Bengal have discovered a pattern of declining fossil diversity that links the eruptions to the extinction.

Researchers have speculated for over 30 years that massive volcanic eruptions in India's Deccan region, about 65 million years ago, poisoned the Earth's atmosphere and eliminated above three-fourths of the world's species. But robust evidence for this theory has remained elusive.

The new study of the Krishna-Godavari basin fossils has shown a stepwise elimination of species after each pulse of volcanic eruptions, a pattern never observed before. The study has appeared this month in the Journal of the Geological Society of India.

"This is the first fossil evidence to suggest a direct cause-and-effect relationship between the Deccan eruptions and the extinction," said Gerta Keller, a professor of geoscience at Princeton University in the US, and the lead investigator of the study.

Keller collaborated with palaeontologists at the Oil and Natural Gas Commission (ONGC), Chennai, and Lausanne University to analyse fossil-bearing sediments extracted through 10 wells in the Krishna-Godavari basin and one in the Bay of Bengal drilled by the ONGC as part of oil exploration work.

The scientists believe their findings fill long-standing gaps relating to the duration of Deccan volcanism and its effect on creatures of that period. Earlier studies have suggested that these eruptions occurred in three distinct phases separated by a few hundred thousand years, but each series of eruptions spewing enormous amounts of lava, at times creating rivers of molten rock stretching 1,500 kilometres to the Krishna-Godavari basin.

The separation of the lava flows over time in the Krishna-Godavari basin gave rise to unique geological layers of fossil-bearing sediments sandwiched between solidified lava.

The fossil analysis by Keller and her team suggests that the diversity of tiny marine organisms in the Krishna-Godavari region reduced from 43 species before the first phase of volcanism 67.4 million years ago to 28 species, and then to 14 species during the second phase about 65 million years ago. Keller worked with the ONGC geologists Bomma Jaiprakash, Adula Reddy, P.K. Bhowmick, H. Upadhyay, A. Dave, and Lausanne palaeontologist Thierry Adatte.

The sediments show a single surviving organism when the second volcanic phase ceased. Keller calls the organismGuembelitria cretacea"disaster opportunist" that, like other surviving species, inherited the world because it could survive extreme stress conditions.

The results again challenge a popular theory proposed in the 1980s that an asteroid striking the Earth caused the mass extinction 65 million years ago.

Keller had also questioned the asteroid theory two years ago showing that the impact took place 300,000 years before the extinction.

"This is a significant finding because it appears to quantify the decline in the species with volcanic pulses," said Ashok Sahni, a senior palaeontologist at the University of Lucknow. But Sahni and others believe the asteroid-or-volcanism debate will continue despite the Krishna-Godavari data.

Last year, an international group of scientists had asserted in the US journal Science that all available research suggests that the asteroid impact at the Chicxulub crater beneath the Yucatan peninsula in Mexico had triggered the mass extinction.

Critics of the Deccan volcanism theory have in the past pointed out that while eruptions release toxic sulfur dioxide, sulfur is removed from the atmosphere continuously and is unlikely to accumulate over long periods of time. They had also pointed out that there is no strong data linking Deccan volcanism pulses to extinction. Some scientists have also questioned the capacity of Deccan volcanism to significantly alter the world's biosphere.

However, Keller and her colleagues have said the second phase of Deccan eruptions would have released 30 to 100 times the amount of sulfur dioxide released by the Chicxulub impact. They say the "kill effect" of Deccan volcanism emerged not just from the volume of gases but the repeated episodes of eruptions and its environmental impacts at great distances from the site of eruptions.

In an independent hypothesis, a US-based palaeontologist of Indian origin Sankar Chatterjee had also proposed several years ago that a second asteroid struck a site near modern-day Mumbai and could have contributed to the extinction.

While large asteroid impacts would also have had environmental consequences, Keller said, they should be seen as the "last straw that broke the camel's back".

Some scientists say the debate over extinction extends beyond its cause.

"There are other unsolved puzzles associated with this extinction," said Guntupalli Prasad, a palaeontologist at the University of Delhi. "It is not clear why only certain groups of organisms became extinct and others didn't," Prasad said.

Crocodiles and turtles, for instance, are among dinosaur-era creatures that survived.

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