Travel Reference
In-Depth Information
laughed. "Let me tell you a secret," he said. "I never liked those Baculites fos-
sils. They all look alike to me. I never bothered to really study the Vancou-
ver Island species." Another torch had been passed. Teacher and student, monk
and acolyte; master and apprentice at the end of a long apprenticeship—
two equals now reveled in one more fact beguiled from nature's grasp. Sucia
became bracketed in time that day.
The long road traveled to arrive at the relative age of this particular
group of rocks is typical not just of Cretaceous rocks but also of rocks and fos-
sil from throughout time. The scientists doing the studying and the times,
rocks, and fossils they study always vary, but the methodology is remarkably
similar. Any study starts with one section of rocks and then expands, even-
tually ending up in a museum. It is an example of nineteenth-century sci-
ence still working well on the threshold of the twenty-first century.
The work of Gabb and others in North America showed that crude but
reliable worldwide correlation of fossil-bearing strata was possible. My work
a century later was one of many confirmations of the efficacy of this type of
time machine. Sedimentary rocks could be dated by studying their fossils.
However, for most other rock types—such as igneous and metamorphic
rocks—assigning any sort of age was impossible before the twentieth century.
The problem was that fossils are found only in sedimentary rocks, never in
igneous or most metamorphic types. Furthermore, even in sedimentary rocks
fossils are only occasionally abundant, and in many sedimentary rocks (such
as glacier, river, and desert deposits) they are never present at all. Some
method other than the use of fossils had to be developed for the purpose of
dating rocks. Ultimately, several such systems were established. The most
commonly used of these newer systems, radiometric dating, is the subject of
the next chapter.
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