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News: Meteor May Not Have Destroyed Dinosaurs Afterall
Dino Deaths Revisited:
Meteor May Not Have
Detroyed Them, After All
By Kenneth Chang
T A L A R N, Spain, Sept. 26 —
Maybe it wasn’t a meteor, after all, that killed off the dinosaurs. According to one paleontologist, dinosaurs continued to live for hundreds of thousands of years after that event, at least in one part of China.
Many paleontologists considered the case of the dinosaur extinction closed as of 65 million years ago, when a large meteor slammed into Earth. Dirt and dust tossed up by the impact blotted the sun, and the resulting chill shoved the dinosaurs into evolutionary oblivion. Geologists had found the equivalent of gunpowder burns — a layer of the radioactive element iridium,
commonly found in meteors — detected in rocks around the world dated to this time.
They even found the gunshot wound - a huge crater off Mexico’s Yucatan peninsula. Except there were a few nagging details that didn’t quite fit the picture.
Other Pieces to the Puzzle
Many believe dinosaurs were already in decline for millions of years before the supposed impact. There was also another suspect — massive volcanic
eruptions that spewed noxious gases into the air and buried much of India in lava flows a couple of miles deep over several million years. Volcanoes can also be a source of iridium. Next theory: Maybe shock waves from the meteor impact traveled through the Earth, triggering the Indian eruptions, which occurred almost exactly at the other side of the planet from the crater site.
That explanation doesn’t work, either. Radiometric dating of the lava flows indicate they started long before the meteor impact. So maybe dinosaurs
were just unlucky. The volcanic eruptions triggered climactic changes that caused their decline, and the meteor impact was just the coup de grace that finished them off.
Now Zikui Zhao of the Institute of Vertebrate Paleoanthropology in Beijing suggests the meteor didn’t even do that. At the First International Symposium of Dinosaur Eggs and Babies in Talarn, Spain Saturday,
Zhao presented evidence of dinosaurs laying eggs long, long after the meteor impact.
Fossilized Eggs Tell Story
Near the town of Nanxiong in southeastern China, Zhao has uncovered numerous nests of fossilized dinosaur eggs.
Because sediments accumulate over time, the lower part of a rock is generally older. And in the lower, older rocks, he found 11 different species of eggs.
The last period of dinosaurs is known as the Cretaceous, the period that follows is the Tertiary, and the time of mass extinctions that divide the two is called the K/T boundary.
At the point in the rocks that Zhao believes corresponds to the K/T boundary, six of the dinosaur species disappear. Eggs of this period also show a spike in levels of iridium, as well as other rare elements.
However, *the remaining five species overstep the boundary and survive,* Zhao says. Indeed, he finds eggs well above the K/T boundary, suggesting that dinosaurs lived for several hundred thousand years longer than
Questions Arise on Dating
Other scientists attending the symposium questioned his dating. *It is not the K/T boundary,* says Nieves Lopez-Martinez of Universidad Complutense in Madrid, Spain. The extinctions and iridium spike, she says, comes from an earlier period of climactic change and possibly volcanic eruptions, about 71 million years ago, which she has detected in rocks in Spain, *not only here, but many other places in the world.*
*He definitely has an anomaly,* says University of Colorado researcher Emily Bray, but she adds, *I think his boundary is too low.* Others were also skeptical, because the rocks surrounding the Nanxiong eggs did not show a rise in iridium amounts.
Zhao counters that his data also shows the earlier, smaller iridium spike and that rivers and rainfall dispersed the iridium over millions of years. The data also argues against the meteor-killed-all-the-dinosaurs scenario, Zhao says. Iridium levels jumped up in three separate spikes near the
K/T boundary, something that could not be caused by a single meteor impact.
Almost half of the eggs near the boundary show defects in their microscopic structure, which Zhao attributes to the high levels of the iridium and other trace elements. And those may be the true dinosaur killers.
*The cause may have been environmental poisoning and adverse changes in climate,* Zhao says, and he points to the massive volcanic eruptions in India as the probable source.
If Zhao’s dating of his eggs proves correct, paleontologists will have to reopen their investigations into what killed the dinosaurs.
Copyright ©1999 ABC News Internet Ventures.
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