[Paleopsych] NYT: Fossils Offer Support for Meteor's Role in Dinosaur Extinction

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Mon Sep 26 23:53:39 UTC 2005

Fossils Offer Support for Meteor's Role in Dinosaur Extinction


    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
    their presence.

    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
    Mexican crater.

    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.

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