Wopmay orogen

The Wopmay orogen is an ancient geological feature located in northern Canada, created when the Bear Plate collided with the Slave Plate during the early Proterozoic.[1][2] It is approximately 500 km along the north-south axis, and 200 km along the east-west axis at its widest point, tapering at both the northern and southern ends.[3]

The formation, also known as the Wopmay Fault Zone, was named for Wilfrid Reid "Wop" May, OBE, DFC (April 20, 1896 – June 21, 1952), a Canadian flying ace in the First World War and a leading post-war aviator.


Formation

Cartoon of a tectonic collision between two continents

The Wopmay Orogen formed ca. 1.9 billion years ago when the Bear plate and the Slave plate collided.[2] Faulting and folding of the four intervening rock zones resulted in a (now eroded) mountain belt.[1] Each of the four rock zones has the typical characteristic of orogenic belts in that they consist of long parallel strips of rock exhibiting similar characteristics along the length of each belt. Orogenic belts are associated with subduction zones. Research from the Lithoprobe project indicates an ancient subduction zone underlying the Wopmay Orogen.[4]

Location

The Wopmay Orogen forms part of the Canadian shield.[1][3] It is located partly in Nunavut and partly in the Northwest Territories in northern Canada, extending eastward from Great Bear Lake, and reaching the Arctic Ocean at Coronation Gulf in the north, and south to Marion Lake (abutting Great Slave Lake).

Significance

Sites such as the Wopmay Orogen provide evidence for early and ongoing plate tectonics. Traces of old oceanic crust, island arcs, and colliding continents indicate that the same forces at work today have been at work in the early Proterozoic and probably earlier. Alignments of magnetic particles in rocks demonstrate that continents were drifting across the surface of the Earth relative to the magnetic poles then as now, and that the ocean floor was rifting and subducting, all at least 1.5 billion years ago.[1][2] This crust cycling is referred to as the supercontinent cycle.[2]

References

  1. 1 2 3 4 Lambert, David (2007). The Field Guide to Geology, New Edition. New York, NY: Checkmark Books. p. 184. ISBN 978-0-8160-6510-3.
  2. 1 2 3 4 Levin, Harold (2006). The Earth Through Time, Eighth Edition. Hoboken, NJ: J. Wiley. pp. Chapter 9, pg 2. ASIN B002T8RFSQ.
  3. 1 2 "Comparisons of the 2005 Geologic Map of North America with the 1965 Map, Areas 1-4; Area 2, Northwestern Canadian Shield". Geology and Environmental Change Science Center. United States Geological Survey (USGS).
  4. ↑ Cook, Frederick. "Probing the Lithosphere of the Wopmay Orogen" (PDF). Calgary, Alberta T2N 1N4: University of Calgary Press, Department of Geology and Geophysics. Retrieved 15 June 2012.

External links

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