Lecture 19 // The Geology of Canada

Question 1

Canadian Shield

Answer 1

The stable interior of the continent is the Canadian Shield. Here Precambrian aged ‘basement rock’ is exposed at the Earth’s surface.
The Canadian Shield (pink & red areas surrounding Hudson Bay) is an amalgamation of small masses of continental crust sutured together during the Archean & Proterozoic. These masses are called Precambrian Provinces.

Question 2

Platform

Answer 2

The craton is comprised of the Canadian Shield and the platform. The platform includes Alberta, southern Saskatchewan, and Hudson Bay.

Question 3

Appalachian Orogenic Belt

Answer 3

The Appalachians arose during end-of-the-Paleozoic suturing of the northern landmass Laurasia and the southern landmass Gondwana.

Question 4

Cordilleran Orogenic Belt

Answer 4

The Cordillera (cor-dee-ehr-ah) is a wide mountain belt that extends from Alaska to the Chilean-tip of South America. Cordilleran Orogenic Belt (Note: we will not be discussing the Inuitian Orogenic Belt)

The vast Cordillera is the result of plate convergence (compression causing tectonic uplift), terrane accretion, and development of fold-and-thrust belts.

Question 5

Rocky Mountains fold-and thrust belt.

Answer 5

Mountain building was greatest during the Cretaceous and Early Cenozoic as accreted terranes were added, building much of British Columbia.

B.C. is composed of 50+ terranes (island arcs, accretionary prisms, oceanic crust, and continental margin rocks displaced along strike slip faults).
In-board stress from accretion resulted in the Rocky Mountains fold-and-thrust belt.

Question 6

Down-flexed area: Western Interior Seaway

Answer 6

The in-board stress not only resulted in the folding and imbricate thrust faults of the Rocky Mountains fold-and thrust belt, but also in an adjacent down-flexed area.

This low-lying area was flooded by the Cretaceous high sea levels. This created the Western Interior Seaway that linked northwards with the Boreal Seaway, and to the south with the Gulfian Seaway.

Question 7

Western Canada Sedimentary Basin

Answer 7

Vast amounts of sediment were eroded from the uplifting Rocky Mountains and shed into the Western Interior Seaway. More and more accommodation room for sediments was made as downwards flexure continued.
 The Western Canada Sedimentary Basin is wedgeshaped, thickest in Alberta and thinning into Saskatchewan. It is from these deposits that huge quantities of oil & gas are recovered.

Question 8

Continental Shelf and Slope

Answer 8

The last of our Canadian geologic provinces is the continental shelf & slope. On the map the contiental shelf (0-200 m) is the grey area that extends from the coastline to the blue line.

Seaward is the continental slope (200-2000 m). The continental slope is the true edge of the continent.
 The continental shelf is narrow on the active western margin, and wide on the passive eastern margin.