INCLINATION CORRECTION FOR THE MOENAVE FORMATION AND WINGATE SANDSTONE: IMPLICATIONS FOR NORTH AMERICA'S APPARENT POLAR WANDER PATH AND COLORADO PLATEAU ROTATION

The ~ 201 Ma paleopole for North America has been observed in two widely different locations, one paleopole is determined from the Mesozoic rift basins in the northeastern US (67ºN, 93.8ºE [Kent & Olsen, 2008]) and one from the Colorado Plateau (CP) (59.8ºN, 75.3ºE [Molina-Garza et al., 2003]). The paleopole from the CP is determined from the Latest Triassic/Earliest Jurassic Moenave Formation and Wingate Sandstone (M&W) of northern Arizona and southern Utah. The discrepancy in paleopole positions has been explained by Kent & Olsen (2008) as due to large amounts of clockwise vertical axis rotation of the CP (13.5º) combined with inclination shallowing of the paleomagnetism; however, structural and geologic data indicate less than 5º of vertical axis rotation for the CP (Gordon et al., 1984; Cather, 1999; Molina-Garza et al., 2003). Inclination shallowing has been corrected for the sedimentary rocks of the northeastern US rift basins, but has not been corrected for the sedimentary rocks from the CP. We resampled the M&W, collecting 5-8 samples from 14 sites that were thermally demagnetized. The formation mean (D = 358.7º, I = 12.2º, a95 = 6.6º) is statistically the same as Molina-Garza et al.’s mean direction. We have corrected the inclination of the M&W rocks to determine if the corrected M&W paleopole from the CP, when unrotated about an Euler pole local to the CP to reconcile the paleopole longitude difference, still has a paleopole latitude difference with the coeval northeastern US paleopole. Based on isothermal remanence anisotropy measurements, the M&W rocks on the CP have experienced inclination shallowing of their paleomagnetic remanence, which changed the M&W paleopole by only ~ 3º northwards. When the inclination shallowing corrected paleopole is rotated 11.5º about an Euler pole local to the CP, the longitudes come into agreement, but there is still a difference ~ 6º in paleopole latitude, although it is not statistically significant. Inclination shallowing cannot reconcile the difference in longitude between the paleopoles. The amount of vertical axis rotation needed to bring the paleopole longitudes into agreement is somewhat smaller than suggested by Kent & Olsen, but still large enough to be inconsistent with the geological observations.