OF CAMP AND CUSP: THE COINCIDENCE OF THE EMPLACEMENT OF THE CAMP LIP AND THE ABRUPT WESTWARD MOTION OF NORTH AMERICA THAT TERMINATED AT THE J-1 CUSP OF THE NA APW PATH

Near the time of the Triassic-Jurassic boundary, the North American plate abruptly began a rapid westward excursion after an extended period of stationary status throughout the Norian Stage of the Late Triassic. This rapid motion terminated sometime after the Hettangian, at which point, the plate reversed direction, returning approximately to its Norian position. The turnaround created the J-1 cusp of the North American (NA) apparent polar wander (APW) curve. The Rhaetian and Hettangian paleopoles from the partially coeval Moenave and Wingate Formations document this westward plate motion. The paleopole of the Hettangian Whitmore Point Member of the Moenave Formation displays the most westward paleopole position, and thus the westernmost position of the NA plate. Whitmore Point lithostratigraphy is truncated by an unconformity, and overlain by the Springdale Sandstone. Paleopoles from the Springdale Sandstone indicate that by the beginning of Springdale deposition, the plate had returned to approximately the same position relative to the geomagnetic pole that it had occupied during the Norian, prior to the Rhaetian-Hettangian excursion. The Springdale Sandstone paleopole is statistically identical to that of the overlying Kayenta Formation, of which the Springdale Sandstone has been speculated to be a part. It is notable that the timing of the onset of the apparent polar motion, hence the onset of rapid westward NA plate motion, is coincident with the emplacement of the Camp large igneous province (LIP). This coincidence of timings leads to the conclusion that the Camp emplacement caused the rapid westward motion of NA.