Travel Reference
In-Depth Information
you know precisely where you are in the geological column: at 83 million
years ago.
The years of field work necessary to complete the mammoth project of
sampling the Italian Apennines yielded more than a detailed look at 100
million years of paleomagnetic reversals. It was from these sections that Wal-
ter Alvarez collected the clay samples that yielded unexpectedly high con-
centrations of iridium—and led to the now-famous hypotheses that the
earth was struck by a large asteroid 65 million years ago and that the global
environmental effects of that impact caused the Cretaceous/Tertiary mass
extinctions, killing off an estimated 60% to 70% of all species then on earth.
An animated controversy arose among earth scientists and lasted more than
a decade. Was this extinction rapid and catastrophic or was it gradual, last-
ing millions of years?
These two great pieces of work—the demonstration of a land-based
section for studying Late Mesozoic and Cenozoic magnetic reversals linked
to biostratigraphy, and the new theory about one of the greatest of all mass
extinctions—caused a tremendous surge of intellectual excitement. Its epi-
center was Berkeley, where Walter Alvarez worked. The late 1970s and early
1980s were aglow with the excitement generated from these two pillars of re-
search. That glow readily made its way 90 miles east to the University of Cal-
ifornia at Davis, where I was still assistant professor of geology. I was swept up
in both fields, and I remain so to this day.
The extinction controversy was by far the more exciting. How could
deciphering the age of west coast rock assemblages compete with dinosaurs
being snuffed out by cosmic collisions? Yet the extinction controversy was
being played out far away, on outcrops in Europe, and in a sense, the first step
to understanding whether the Alvarez theory was correct in determining the
age of the rocks in question. Nevertheless, it was with some wistfulness that
I resigned myself to working in the wings, while others lept to center stage as
the extinction drama unfolded in nearby Berkeley. Chance would soon
change that for me.
In the century since William Gabb had made the first discoveries of
Cretaceous-aged rocks in California, so much had changed. The Indians
