Series of mountain-building events that affected much of western North America in Late Cretaceous and Early Paleogene time (c. 65.5 million years ago). The Laramide orogeny originally was believed to mark the Cretaceous-Paleogene boundary. It is now considered to have consisted of many separate pulses of deformation that varied in intensity and age from place to place. Laramide rocks, however, were generally created around the Cretaceous-Paleogene time boundary.
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