PreCambrian Shield

The Precambrian shield in Manitoba is divided into 2 geological or structural provinces. The Archean rocks of the Superior Province, the oldest known in the shield, have an easterly structural grain and were involved in the Kenoran mountain building that ended approximately 2.5 B years ago. Isotopic studies of these rocks indicate they were formed 2.5-3.0B years ago.

To the northwest, the Churchill Province contains Proterozoic and Archean rocks that were involved in the Hudsonian mountain building, which ended approximately 1.7B years ago, and exhibit both an easterly and northeasterly structural grain. Isotopic ages for these rocks range from 1.7-3.3B years.

A highly deformed boundary zone, where the 2 provinces meet, is characterized by complexly interfolded and faulted ARchean gneisses and some supracrustal Proterozoic rocks. Throughout most of Manitoba, the Precambrian shield was reduced to an almost featureless plain by the time the initial sediments of the Phanerozoic era were deposited.

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