Dino-killing meteorite did not start global wildfires 65 million years ago

February 24th, 2009 - 2:58 pm ICT by ANI  

London, Feb 24 (ANI): The results of a new research indicate that the dinosaur-killing meteorite that struck Earth at the end of the Cretaceous period 65 million years ago did not start global wildfires.

The impact of a huge meteorite at the end of the Cretaceous period 65 million years ago is generally held responsible for the sudden demise of 6080 percent of all species on Earth.

But, according to a report in Nature News, new results challenge the common idea that the extinctions were partly caused by global wildfires triggered by the violent impact.

Researcher Claire Belcher and colleagues at Royal Holloway University of London in Surrey, UK, have said that the widespread soot deposits in sedimentary rocks formed at the time of the putative impact are not, as previously asserted, evidence of runaway fires caused by the meteorites impact.

They have analysed the mixtures of carbon-based molecules called polycyclic aromatic hydrocarbons (PAHs) in the sooty material from these rocks, and find that the compositions of the mixtures dont match those typically produced by burning vegetation.

Instead, they resemble those formed when hydrocarbons such as gas and oil are burnt.

The researchers think the soot comes from combustion of hydrocarbons within the rocks of the impact site itself thought to be the region around Chicxulub on the north coast of the Mexican Yucatan peninsula, where a now partly submerged crater about 180 km across has been dated to the time of the mass extinction that separates the Cretaceous from the Tertiary period.

For several years now, Belcher and her colleagues have been casting doubt on the idea that the Earth was engulfed in flames for years after the impact.

In 2003, they reported that rock strata in North America dating to the CretaceousTertiary boundary showed little evidence of charcoal, which would be expected to be produced from burning vegetation.

Instead, they speculated that the soot in these layers came from combustion of hydrocarbons.

Now, the team claim to have clinching proof of that: chemical fingerprints of the source of the soot, in the form of 21 different PAHs separated and identified using the technique of gas chromatography.

According to Belcher, the new results also answer criticisms of their earlier work on the apparent lack of charcoal in the soot.

The soot itself undoubtedly had a significant impact on life at the time, but it is unlikely to represent the signature of global wildfires, said Belcher. (ANI)

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