CAN DIFFERENCES BETWEEN LATEST TRIASSIC TO EARLIEST JURASSIC PALEOMAGNETIC DATA FROM THE AMERICAN SOUTHWEST AND EASTERN NORTH AMERICA BE RESOLVED?

Latest Triassic to earliest Jurassic paleomagnetic pole positions from the American Southwest are located near 61° N/62° E while poles from northeast US rocks are located near 67° N/94° E. This difference in pole positions has fueled debate concerning the position of North American from latest Triassic to earliest Jurassic. A flattening factor of 0.5 (elongation/inclination method) results in a correction of ~14° to data from Newark/Hartford basins rocks. If data of similar age from the American SW were corrected by the same flattening factor (0.5) as well as ~10°-15° of clockwise rotation of the Colorado Plateau, pole positions from the two regions essentially coincide. Any correction for inclination bias, ideally, should be based on data from specific rocks sampled. We obtain new paleomagnetic data and examine inclination bias (elongation/inclination method) of the latest Triassic to earliest Jurassic Moenave Formation to test the hypothesis that the disagreement between pole positions between these and Newark/Hartford rocks is not an artifact of inclination bias as well as Colorado Plateau rotation. Strata of the Moenave Formation yield a mean inclination after structural correction of 7.9° (N = 56 sites from 4 localities). The data set, based on 450 samples, provides an elongation of 2.7, a flattening factor of 0.7, and a corrected formation mean inclination of 10.8°. This flattening factor differs from strata from the Newark/Harford basins. A new paleomagnetic pole of 63.9° N, 59.2° E (A95 = 4.6°) for the Moenave Formation is based on our new data and a grand pole for Moenave Formation is 62.4° N, 60.4° E (A95 = 2.8°, N = 107 sites), with all sites mean directions corrected using a flattening factor of 0.7. The average Moenave Formation pole lies 4.2° south and 32.4° west of the Newark/Hartford pole. The angular distance between the grand Moenave Formation pole and the Newark/Hartford pole exceeds the magnitude of clockwise rotation that can be realistically accommodated by compressional structures on the eastern and northern boundaries of the Colorado Plateau. We interpret that inclination bias coupled with Colorado Plateau rotation are not sufficient to bring poles from these two areas in agreement.