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magazine / ja07

July/August 2007 issue


Tintina Trench

Fault zone
A massive geological scar slicing diagonally across the Yukon, the Tintina Trench is a rich and largely untouched wildlife corridor of staggering abundance
Photography by Patrice Halley with text by Andrew Findlay

A photo gallery tour of the Yukon's Tintina Trench, which slices diagonally across the territory from Alaska to British Columbia, tracing one of the world's major fault zones.
Only if you were suspended in space could you fully appreciate the geological scale of the Tintina Trench. It is painted on the Yukon map like a crude brush stroke on a tattered canvas, running nearly 1,000 kilometres from the Liard Plateau at the British Columbia border to Alaska's Woodchopper Creek. Yet here on Earth, northwestward through the trench toward the Yukon River, it is difficult to fathom the fault line deep below that marks the edge of an ancient North American continent.

On a gusty summer afternoon, photographer Patrice Halley and I wander up to the cloud-covered alpine tundra below Mount Mye, in the Anvil Range. Cold mist rolls across the landscape as we perch on the edge of a geological marvel that forms a wildlife corridor of staggering abundance and also bears the imprint of human migration and settlement dating back thousands of years. Thickets of willow, the leaves already displaying rusty hues of autumn, become fleeting images in the restless air. Under our feet is a thick carpet of moss and lichen. Delicate coral-like shoots of sieve cup lichen and grey reindeer lichen cushion our steps. Pausing atop a granite boulder, we scan for a glimpse of Fannin's sheep, one of Tintina's wildlife curiosities. I press my boot against the rock and ponder the history concealed in the silent ground.

Click map to enlarge
Between 120 million and 190 million years ago, the convergence of tectonic plates forced land masses of igneous origin from the west to attach to the much older rocks of North America - some 300 million to 1.8 billion years old - as the continent merged with offshore volcanic islands. In the same period, the land now occupied by Whitehorse was submerged beneath a deep marine basin which gradually filled up with sediments. About 100 million years ago, dinosaurs roamed the freshly formed uplands in what is now the Yukon. About 60 million years ago, after the sea drained away, plates on the south side of the trench began a torturous 450-kilometre journey to the northwest. By the time this massive shift was over, rocks once located in northeastern British Columbia had come to rest where the Pelly Mountains stand today, across the trench from the Anvil Range.

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