IS THE COLORADO PLATEAU RESPONSIBLE FOR THE ANCESTRAL ROCKIES?

Numerous geologic events assembled from the literature and from personal research suggest that the Colorado Plateau may have maintained a quasi-independent identity relative to the rest of the North American craton since sometime in the Proterozoic. Both subduction and rifting events may have affected the Plateau's northern border during different parts of the Proterozic. During the Pennsylvanian-Permian, compression along both the northern border and the eastern border occurred along with paleomagnetic suggestions of a rotation of the Plateau relative to cratonic North America. Paleomagnetism again suggests rotation in the Late Jurassic (ca. 150 Ma). Rotational compression of the Plateau clockwise into the craton also has been suggested to have caused the Laramide deformation of the craton during the Cretaceous. Eocene compression of the northern border of the Plateau against the Wyoming Province caused the uplift of the Unita Mountains while Rio Grande rifting occurred on the eastern border, inducing further minor clockwise rotation. In between tectonic events, sedimentation proceeded across these boundaries, making the Plateau appear to be contiguous with the North American craton. The geologic and paleomagnetic evidence will be summarized in an effort to understand whether these numerous tectonic events involving Plateau boundaries and spanning a large amount of geologic time indicate the long-term existence of an independent microplate that has been involved in the deformation of the western North American craton.