FIGURE 2.2 Simplified geological map of Virginia. Virginia’s geology is extremely diverse, resulting from a long geological evolution starting at least some 1.44 billion years (Ga) ago with Proterozoic rocks in the Blue Ridge and Western Piedmont provinces, through four successive episodes of mountain building (orogenic cycles): the Grenville Orogeny at about 1.1 Ga, the Taconic Orogeny at about 0.45 Ga, the Acadian Orogeny at about 0.38 Ga, and finally the Alleghenian Orogeny at about 0.32 Ga. SOURCE: Modified from Bailey (1999b).

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