Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: FRIDAY, September 8, 1995 TAG: 9509080100
SECTION: NATIONAL/INTERNATIONAL PAGE: A-6 EDITION: METRO
SOURCE: Associated Press
DATELINE: WASHINGTON LENGTH: Medium
Precise dating of geologic samples that mark the extinction 250 million years ago show the massive die-off occurred about the same time a volcanic eruption blanketed Siberia with lava and filled the global sky with chemicals, scientists report Friday in the journal Science.
``We have been able to put a very precise date on the extinction boundary [formation], something that has not been done before,'' said Mark Richards, a University of California, Berkeley, professor of geophysics and co-author of the study.
The date of that extinction, which marks the shift from the Permian to the Triassic period, was the same, within a few thousand years, as the Siberian eruptions.
Paul Renne, director of the Berkeley Geochronology Center and also a co-author, said the extreme volcanic activity may have set off events that killed 90 percent of all marine species and 70 percent of all land vertebrates, along with most of the terrestrial plant life.
Animals killed in the Permian extinction were less well-known than the dinosaurs. The victims were such things as clams, sponges and trilobites, a type of armored sea animal.
In the study, the authors speculate that just before the lava started flowing, the Siberia ground would have risen by several hundred yards over hundreds of miles, setting off an ice age by forcing formation of vast glaciers.
``A short-lived volcanic winter followed within several hundred thousand years by greenhouse conditions would fully explain the environmental extreme that caused the ... mass extinctions,'' the study says.
by CNB