Coeval formations on both the North American craton and Colorado Plateau have been sampled for the comparison of paleomagnetic pole positions. The latest Pennsylvanian-earliest Permian Laborcita and the Early Perman Abo formations of eastern New Mexico, and the latest Pennsylvanian Wescogame Formation of the Supai Group of northwestern Arizona were studied. Thermal demagnetization demonstrated that the majority of the samples in all three formations were remarkably free of significant secondary overprinting. Computation of the pole positions used only samples which exhibited univectorial decay to the origin over at least three or more temperature steps. The paleopole of the Wescogame Formation is 119.2 ¿E, 47.3 ¿N (N=45 samples, k=41.6, dp=1.7, and dm=3.4); the Laborcita Formation paleopole is 130.6 ¿E, 41.8 ¿N (N=114 samples, k=42.9, dp=1.0, and dm=2.0); and the overlying Abo Formation paleopole is 118.3 ¿E, 49.7 ¿N (N=84 samples, k=54.9, dp=1.1, and dm=2.1). Comparison of the Wescogame, Laborcita, Abo and other paleopoles of this age shows the plateau poles displaced clockwise, confirming a clockwise rotation of the Colorado Plateau with respect to stable North America.

The new data could be interpreted to indicate a 7¿¿4¿ rotation of the plateau; however, the direction of displacement of Pennsylvanian and Permian paleopoles is significantly different from that exhibited by the Early and the Late Triassic poles. The current body of data is best fit by not one, but two, rotations and suggests that the Colorado Plateau rotated in Late Permian time, prior to later, presumably Laramide, rotation. Separate calculations of the Late Permian rotation, from Late Pennsylvanian data and from Early Permian data, both indicate a rotation of about 9.5¿¿2.7¿ northward and 5.4¿¿2.7¿ westward. This study thus suggests that at least two rotations of the Colorado Plateau have occurred prior to the most recent rotation involving the opening of the Rio Grande Rift. This history of rotations implies a quasi-independent plate motion behavior for the Colorado Plateau microplate. ¿ American Geophysical Union 1988