Bedrock Geology

Bedrock is the solid rock under the deposits of soil, sand, clay and gravel on the earth's surface. Thousands of metres of bedrock formations underlie Alberta, containing fossil fuels (oil, coal and natural gas), salt, limestone, sulphur and groundwater. The Precambrian formation, the oldest of these rocks, makes up Alberta's "basement".

Canadian Shield


Composed of Precambrian rock that includes granite, gneiss and quartzite, the Canadian Shield is only visible at the surface in the northeast corner of Alberta. This visible portion makes up approximately three per cent of Alberta's land cover. The Shield does in fact underlie all of Alberta's plains and mountains, forming a sloping foundation for the province, at its deepest point six km below the surface.

Interior Plains


Rocks underlying the Interior Plains form a wedge, decreasing eastward where it meets the exposed Canadian Shield. This bedrock wedge is otherwise only exposed along deeply eroded river valleys. In most cases, it is covered by a surface layer of sediment that was deposited by glaciers. This rock wedge contains much of Alberta's petroleum, coal and oil sand resources.

Bedrock of the Interior Plains consists of older Devonian limestones located near the Canadian Shield and the younger Cretaceous and Tertiary shale and sandstone that extend eastward from the Foothills. Youngest to oldest, these formations include:

  • Tertiary (sandstone, shale and coal)
  • Upper Cretaceous (sandstone, coal and bentonite)
  • Lower Cretaceous (shale and oil sands)
  • Devonian (oil, gas, limestone, dolomite, rock salt and gypsum)

Rocky Mountains and Foothills

Composed of Paleozoic and Precambrian sedimentary rocks such as sandstone, shale, limestone, coal and gypsum, these formations are like those underlying the Interior Plains.

See the Atlas of Alberta for a map of the bedrock geology, or visit:

 

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Updated: Feb 5, 2015