[Paleopsych] NYT: Fossils Offer Support for Meteor's Role in Dinosaur Extinction
checker at panix.com
Mon Sep 26 23:53:39 UTC 2005
Fossils Offer Support for Meteor's Role in Dinosaur Extinction
By WILLIAM J. BROAD
No guns materialized. Even so, the scientists kept a low profile while
digging, eager to avoid security forces from the nearby air base - an
important military site that helped provoke the Cuban missile crisis.
The diggers had no permit and no interest in being asked to explain
In the end, they found rare fossils that are shedding new light on
what wiped out the dinosaurs at the end of the Cretaceous period 65
million years ago.
For more than a decade, the standard view has envisioned a speeding
object from space that crashed into the earth and kicked up enough
dust and rock around the globe to blot out the sun. The smoking gun
seemed to be the discovery beneath the Yucatán peninsula of Mexico of
a 110-mile-wide crater called Chicxulub, after a nearby town.
But lately, doubters have argued that Chicxulub formed 300,000 years
before the mass extinction - too early to have played a role in the
demise of the dinosaurs and hundreds of other plant and animal species
that vanished at the end of the Cretaceous.
The team of scientists zeroed in on Cuba as an ideal place to seek
clues, having heard from Cuban colleagues of a possible trove of
fossils of the right age. The Cuban zone was 600 miles from the
Now, in the September issue of Geology, the scientists, from Spain,
Cuba and Mexico, report that they have discovered a highly disturbed
bed of fossils that bears numerous signatures of Chicxulub's mayhem.
The date of the disturbance, 65 million years ago, is exactly at the
end of the Cretaceous.
"It's basic" to resolving the debate, Laia Alegret, a team geologist
at the University of Zaragoza in Spain, said in an interview. "But it
was difficult. The site is located opposite a military base. So it's
almost impossible to get a work permit."
The discovery was outside Santa Clara, a city in central Cuba whose
nearby air base drew scrutiny in 1962 when American spy planes spotted
Soviet jets and antiaircraft missiles. It turned out that the base
held Soviet bombers and a half-dozen atom bombs.
"It was definitely a hot spot," said Timothy Naftali, a cold war
historian at the University of Virginia.
Starting around 2000, Dr. Alegret and her European colleagues
repeatedly sought work permits for a nearby hill but always met with
stultifying delays, if not outright rejections. Finally, they slipped
into the site with their Cuban colleagues, going in late 2000, 2002
and 2003. At other times, the Cubans went in alone.
A rocky outcrop on the hill showed an exposed bed of sedimentary rock
made up of broken bits of minerals and fossils. It was more than 30
feet thick. The team took 66 samples. Examination with microscopes
showed numerous signs of cosmic violence, including quartz deformed by
high temperatures and pressures, as well as tiny spheres of glass,
both clearly debris from a spectacular fireball.
Microscopic study also revealed the presence of thousands of tiny
fossil creatures, most especially foraminifera. Those one-celled
animals have a bewildering array of minuscule shells. Forams, as they
are known, evolve so fast that geologists, paleontologists and oil
companies use their shifting appearance as reliable guides to geologic
"They told the age of the sediments," Dr. Alegret said. "So we've
definitely confirmed the age of these deposits."
At the end of the Cretaceous, the rocky bed now in Cuba formed on the
ocean bottom at a depth of perhaps 3,300 feet, over a few days or
weeks as tons of debris rained down from the sky and huge waves
generated by the Chicxulub event washed land out to sea.
"It was geologically instantaneous," Dr. Alegret said of the deposit's
Earth movements over the ages turned that part of the seabed into
Dr. Alegret's co-authors include Ignacio Arenillas, José A. Arz,
Alfonso Meléndez, Eustoquio Molina and Ana R. Soria of the University
of Zaragoza; Consuelo Díaz of the Institute of Geology and
Paleontology in Havana; José M. Grajales-Nishimura of the Mexican
Institute of Petroleum in Mexico City; and Reinaldo Rojas of the
National Museum of Natural History in Havana.
Dr. Alegret said that because of the site's importance, her Cuban
colleagues were talking with the government to have it protected from
rain and erosion. The aim is to save the outcrop for scientific study.
More information about the paleopsych