The western part of the Guayana Shield s at least as old as 1200 m.y. where it is exposed in the Guaviare River valley in Colombia. Subsequent rogenic events west of the Shield area include the evelopment of the Macarena Mountains, which reflect nearby basement age values ranging from 445 to 495 m.y., and the development of a north-south arch in Northern Colombia, uplifted and folded in Cretaceous and Tertiary times, agreeing with an age value of 110 m.y.

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