- Jan 7, 2002
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Scientists have cast doubt on the well-established theory that a single, massive asteroid strike killed off the dinosaurs 65 million years ago.
New data suggests the Chicxulub crater in Mexico, supposedly created by the collision, predates the extinction of the dinosaurs by about 300,000 years.
The authors say this impact did not wipe out the creatures, rather two or more collisions could have been responsible.
The report is published in Proceedings of the National Academy of Sciences.
An international group of scientists led by Professor Gerta Keller, of Princeton University, US, looked at a continuous sequence of rock - a core - drilled out of the Chicxulub structure.
They analysed rock from this core using five separate indicators of age, including fossil planktonic organisms and patterns of reversals in the Earth's magnetic field.
The results suggest the 180-km wide crater was punched into the Earth 300,000 years before the dinosaurs disappeared from the face of the planet.
At numerous sites around the world, a clay layer separates rocks laid down in the Cretaceous Period from those deposited in the Tertiary and is known as the K-T boundary.
It marks the point in time when the dinosaurs died out and was first linked to the Chicxulub crater in 1991.
The researchers contend their findings prove the Chicxulub impact did not by itself trigger the extinction of the great beasts.
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New data suggests the Chicxulub crater in Mexico, supposedly created by the collision, predates the extinction of the dinosaurs by about 300,000 years.
The authors say this impact did not wipe out the creatures, rather two or more collisions could have been responsible.
The report is published in Proceedings of the National Academy of Sciences.
An international group of scientists led by Professor Gerta Keller, of Princeton University, US, looked at a continuous sequence of rock - a core - drilled out of the Chicxulub structure.
They analysed rock from this core using five separate indicators of age, including fossil planktonic organisms and patterns of reversals in the Earth's magnetic field.
The results suggest the 180-km wide crater was punched into the Earth 300,000 years before the dinosaurs disappeared from the face of the planet.
At numerous sites around the world, a clay layer separates rocks laid down in the Cretaceous Period from those deposited in the Tertiary and is known as the K-T boundary.
It marks the point in time when the dinosaurs died out and was first linked to the Chicxulub crater in 1991.
The researchers contend their findings prove the Chicxulub impact did not by itself trigger the extinction of the great beasts.
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