Large areas of exposed basement rocks in a craton,
typically surrounded by flat-lying or gently dipping platformal
deposits that either onlap or were eroded from the shield area.
Almost all shields expose Precambrian rocks, and most are
comprised dominantly of Archean rocks. One of the best
known shields is the Canadian Shield, where Archean and Proterozoic
cratons and orogenic belts are exposed across a huge
expanse of generally low-relief but rugged hills across central,
eastern, and northern Canada and Nunavut, and surrounded
by gently dipping Phanerozoic sequences of the North American
platform. Other well-known shields include the Guinea
Shield, the Arabian-Nubian Shield, and the Indian Shield.
See also CRATONS.
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