ROANOKE TIMES
Copyright (c) 1996, Roanoke Times
DATE: Tuesday, July 30, 1996 TAG: 9607300102
SECTION: NATL/INTLL PAGE: C-4 EDITION: METRO
SOURCE: The New York Times
A VIRGINIA TECH PROFESSOR and others suggest that soda water killed dinosaurs' predecessors.
Around 250 million years ago, something so devastating occurred that about 90 percent of Earth's animal species were wiped out.
While the cause of this greatest of all mass extinctions remains uncertain, a new study by biologists and geochemists suggests that a huge upwelling of carbonated water from the depths of the oceans may have played a lethal role.
That mass extinction, at the end of the Permian period, reshuffled Earth's genetic deck, making way for the rise of dinosaurs in the subsequent Mesozoic era.
The Permian ``great dying'' wiped out nearly all ocean life and took a heavy toll on land animals.
Much of the fossil record of the period has been erased by time, but scientists agree its causes were different from those that killed the dinosaurs 185 million years later.
A popular theory of the dinosaur extinctions 65 million years ago is that an asteroid or comet hit Earth, drastically changing the global climate. The theory is supported in part by the discovery of high levels of iridium in sediments marking the end of the Mesozoic era - levels more consistent with the iridium content of asteroids than with terrestrial soil.
But no such iridium anomalies associated with the Permian extinction have been found, and
Another theory for the Permian mass extinction is that a gigantic volcanic eruption covered much of present-day Siberia with lava.
The newest idea is proposed in a report published in the current issue of the journal Science by four scientists: Dr. Andrew H. Knoll of Harvard University's Botanical Museum; Dr. Richard K. Bambach, a geologist at Virginia Tech; Dr. Donald E. Canfield of the Max Planck Institute for Marine Microbiology in Bremen, Germany; and Dr. John P. Grotzinger, a planetary scientist at the Massachusetts Institute of Technology.
The researchers argue that the patterns of extinctions and of the types of calcium-carbonate sediments laid down at the end of the Permian period are consistent with a global turnover of deep ocean water, which would have brought immense amounts of carbon dioxide to the surface.
Although some carbon dioxide is always present, too much of it can kill animals, particularly marine organisms.
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