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The Geological Time Scale
Rocks representing most of these time periods are found in Alberta. The best way for geologists to see subsurface rocks in their proper sequence is to look at oil well drill cores. Normally, the well starts in younger rocks and cuts through successively older rocks, and if one continued drilling, the Precambrian basement of Alberta would eventually be reached. During the drilling process, rock fragments are brought to the surface and identified by a geologist. These rocks are used to produce a diagram, called a rock column, that shows rock types, thicknesses, and fossils. Related rock layers are grouped into formations and given a name. Formations are often combined into larger entities called groups. Formations are the basic rock unit that geologists use when they make geological maps. Reprinted from A Traveller's Guide to Geological Wonders in Alberta by Ron Mussieux and Marilyn Nelson with the kind permission of the authors and the Provincial Museum of Alberta. |
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Updated October 16, 2001 by DM |