Haskin's MA thesis breaks new ground

Jun 12, 2003, vol. 27, no. 4
By Carol Thorbes

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Could south-central B.C. have once been an oasis of graceful palm trees and sumptuous Mexican fruit?

Perhaps, according to a Simon Fraser University graduate's master's thesis, which is leading scientists to re-evaluate their understanding of the tectonic history of western North America.

(Tectonic refers to the structural movement of the earth's crust.)

Michelle Haskin (left) was recently awarded the Jack Henderson prize for her controversial thesis in earth sciences, completed at SFU in 2001.
The structure and tectonics division of the Geological Association of Canada bestows the national award for excellence in master's or doctoral research.

Haskin created a cutting edge tectonic model in the hopes of reconciling two long-standing, conflicting theories about the movement of terranes that now form much of western B.C. Terranes are gigantic, mobile pieces of the earth's crust.

The terranes in Haskin's study covered an area 2,500 kilometres long and 500 kilometres wide.

Paleomagnetic data indicates the terranes travelled 3,000 kilometres, along a San Andreas-style fault system, from Baja Mexico to their current place near Williams Lake, between 100 to 55 million years ago. Paleomagnetism uses the orientation of magnetic grains in rocks to assess their latitudinal origin.

Geologic data tells a different story. It puts the travel distance at less than 1,000 kilometres over the same time period, making the place of origin northern California.

Many researchers have supported one or the other model, creating a huge rift between them.

Haskin reaffirmed the accuracy of both theories separately.
But when she integrated both data sets into a single model her results were astonishing.

Tectonic plates beneath the terranes would have had to move at a rate of 38 centimetres a year for their original location to be Baja Mexico.

“Given that the fastest documented plate velocities are roughly half that rate, we need to either re-evaluate the accuracy of paleomagnetic versus geologic methodologies or better understand tectonic movement,” says Haskin.

Her controversial findings raise the scientific bar in tectonic research. “If the combined paleomagnetic and geologic location of such a large crustal block is contentious then,” says the UBC earth sciences instructor, “there could potentially be other places where there are similar problems.”

Haskin's former principal thesis supervisor, SFU earth sciences associate professor Peter Mustard, says her Jack Henderson prize is truly an honour.

“It is awarded by an elite group of scientists in tectonics evaluating the student's direct research contribution, not just the grade point average or other non-subjective evaluations.”

Haskin wrote two articles about her research for the April issue (2003) of the Journal of Geophysical Research.

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