Travel Reference
In-Depth Information
According to all studies, the southern limit of Baja British Columbia is
found in the San Juan Islands of northern Washington state. In fact, Sucia
Island may mark one bit of this southern boundary. The rocks making up the
fossiliferous portions of Sucia, as well as other parts of the Upper Cretaceous
Nanaimo Group of the Vancouver Island region, suddenly became critical
elements if this idea of a drifting subcontinent smashing into North America
was to be tested. Mt. Stuart, 100 million years old, seemingly obtained its
magnetic signal somewhere in the latitude of Mexico. The Eocene rocks of
northern Washington seem to have originated at a latitude similar to that of
their present location. The rocks of intermediate age, the fossiliferous rocks
of the Nanaimo Group—including Sucia Island—would seem to hold the
key. Two teams of American and Canadian scientists, led by Merle Beck and
Ted Irving, quickly began to sample the rocks of the Vancouver Island region.
Here, surely, would be the key to unraveling—confirming or refuting—the
mystery of Baja British Columbia. Did it exist at all? How much drift took
place? To their dismay, they found only nonsensical results. The problem,
again, was reheating.
Magnetic crystals locked in rocks provide the compasses that reveal
ancient pole positions. However, if the rocks in which they sit are reheated,
the force lines of the magnetic field change orientation at the time of re-
heating. All previous information is erased, or overprinted. Sometime in
the early Tertiary Period, perhaps 50 million years ago, large portions of
Vancouver Island were reheated. The cause of this heating is poorly under-
stood. Perhaps the island ran over a hot spot, or perhaps regional volcan-
ism simply heated larger parts of the region. The result, in any case, was
to scramble the precious magnetic information locked in the rocks—
information that could have been the decisive test of drift history. Because
of this, it was soon widely thought that no reliable magnetic signal would
ever be recovered from the Vancouver Island region. The paleomagnetic re-
sults from my drilling on Hornby Island in 1986 only seemed to confirm this
view. But as so often happens in science, a chance event would alter this
perception.
