Travel Reference
In-Depth Information
years ago did indeed end the Age of Dinosaurs. But the primary goal here was
to bring home several hundred magnetic cores for paleomagnetic analysis.
We flew home, finally, laden with rocks and the many cores. With im-
patience 1 awaited the paleomagnetic results. First, the cores had to be
trimmed, and then one by one they were fed into the magnetometer, over
and over, as many as 10 times per cote. It soon became discouragingly clear
the these cores were far more compromised by magnetic overprint than any-
thing we had collected in California; in fact, it turned out that
none
of the
cores was useful for paleomagnetics. These rocks had apparently been re-
heated, the small magnetic crystals in the cores realigned with a much
younger magnetic field. The weeks of work were for naught. We had hoped
that the Spanish rocks would have the same pristine magnetic signal as those
from California, hut we were wrong. Several years later, Dr. Jan Smit of Hol-
land would try again to drill Zumaya. I told him about our disappointment.
Yet he too refused to believe that these rocks would not yield good paleo-
magnetic results. He too understood the importance of learning the position
of the paleomag reversal in the uppermost Cretaceous at Zumaya. And he
too would conclude, as I had, that a magnetic overprint had forever de-
stroyed the primary magnetic signal hete. There is no publication of negative
results of this kind.
The work in Spain taught me a hard lesson. Magnetic clocks are reliable
only in special circumstances. When they work, they are superb. But there is
no way you can go up to an outcrop and be sure that you will obtain results.
By the end of 1984, a magnetic reversal had been identified from the
Cretaceous of California. But the Nanaimo Group still tightly guarded the
secret of its age. Other workers before me had tried to extract its magnetic
time secrets; others had tried to use the time machine of a magnetic clock.
No one had succeeded. Spain had taught me caution, and I wondered
whether magnetic sampling of Vancouver Island was worth the effort. But
the reward if it worked! Magnetic analyses tell you more than time: They
can pinpoint the ancient position of the rocks you study, the latitude at
which the sedimentary or volcanic rocks solidified. They can be the best tool
of all for fixing
place.
The rocks we had drilled in California and Spain had
