Geoscience Reference
In-Depth Information
M
YSTERIOUS
S
PHERULES
While working on the iridium-rich K-T boundary clay at Caravaca,
Spain, in 1981, Jan Smit and G. Klaver discovered rounded, sand-
sized grains of feldspar.
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2
Similar spherules showed up at the other
prominent K-T sites and in several deep-sea cores that captured
the boundary. On the basis of the mineralogy and texture of the
spherules, Smit, Alessandro Montanari, the Alvarezes, and their col-
leagues concluded that they were congealed droplets of molten
material that had been blasted aloft in the K-T impact explosion.
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3
Wezel and his group reported that, like iridium, the spherules
spread out above and below the K-T boundary at Gubbio, undercut-
ting the claim for a special event at the boundary.
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4
Officer and two
colleagues from Dartmouth wrote that they had found spherules
over a vertical span of rock at Gubbio equivalent to 22 million years,
analogous to their alleged findings of spread-out iridium.
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5
The
Wezel claim led to one of the more bizarre episodes in the debates
over the Alvarez theory, which is saying a lot. Officer presented
Wezel's results at the 1985 meeting of the American Geophysical
Union, but Montanari, who had also collected and studied the Gub-
bio spherules, came up with quite a different interpretation of what
Wezel and company had found, which he then shared with his col-
league, Walter Alvarez. Let us pick up the story in the words of the
protagonists, as reported by Malcolm Browne in the
New York Times
of January 19, 1988:
But according to Dr. Alvarez, "My son Walt took just two minutes to
demolish Officer after he delivered that paper." Dr. Alvarez said his son
showed that the "spherules" found by Dr. Officer's team were merely
insect eggs and had been mistaken for mineral spherules because they
were not cleaned well enough. "At that point," Dr. Alvarez wrote in his
autobiography, "the audience of several hundred Earth scientists burst into
laughter, something I'd never witnessed before in my 53 years of attending
scientific meetings."
Dr. Officer responded: "This is a misstatement. There was no outburst
of laughter following Walter's brief comment, and no direct or implied
derision of me as a scientist by the audience." "My talk at that meeting,"
he said, "concerned the hypothesis that intense volcanic activity and the
lowering of sea levels explains the mass extinctions at the end of the Cre-
taceous. During that talk, mention was made of the distribution of
microspherules. Walter had kindly pointed out to us previously that there
were contaminant hollow spherules of recent origin as well as solid
spherules of a mineral composition indigenous to the geologic section."
