Travel Reference
In-Depth Information
understand the past—the principle of uniformitarianism—is one of the most
powerful of all time machines.
All too soon it was over. Air exhausted, our small group of divers re-
treated again to our native land. After the dive I chatted with one of the other
divers, and he asked the usual questions of a stranger, including the inevitable
"What do you do?" I told him that I was a beginning graduate student in pale-
ontology and had been assigned to study whale fossils from the Washington
state seacoast. The only trouble was that despite arduous searching, I had yet to
find
.1
single whale fossil and
was
rapidly getting discouraged. The man told me
that he was an amateur paleontologist. He had never looked for whales, but he
had been collecting fossils from Sucia Island for many years and had a large col-
lection that he would give me if I wished. Apparently, I had reached a fork in
my career path—one direction leading to the study of the Cenozoic Era and its
whales, the other leading back into deeper time, toward the Mesozoic Era and
its ammonites, nautiloids, and dinosaurs. On that day I took the latter route.
My new friend was as good as his word. Within a week an enormous
collection of fossils, all meticulously cleaned, numbered, and their collection
locations noted (in short, all the hardest work done), arrived in my tiny cu-
bicle of an office. Nearly all fossils resembled the modern-day nautilus but
were far more ornate. They were fossil ammonites, extinct relatives of the
chambered nautilus and the first I had ever seen apart from the poor, scrubby
examples in our classroom teaching set. The ammonites from Sucia are iri-
descent, large, exquisite. They and their kind—I thought then—are also
akin to ancient stone wrist watches. All I had to do was look in some book
and identify the species of ammonites from Sucia Island, and I would find the
age of the sediments where they had been collected. What could be easier?
The fossils all had numbers and could be keyed into a map. But know-
ing the geographic position of each fossil-collecting locality was not enough
for me to come up with any sense of age. Their
stratigraphic
position was what
I needed. Stratigraphy is the study of layered rocks and of the relative ages of
strata. Nearly all fossils come from layered rocks, and each layer in a sedi-
mentary succession sits upon one slightly older. Because Sucia is made up of
