Paleomagnetic data from Triassic strata, Zuni uplift, New Mexico: Further evidence of large‐magnitude Triassic apparent polar wander of North America

Abstract

Upper Carnian (∼225 Ma) strata of the Bluewater Creek Formation of the Chinle Group of the Colorado Plateau, western New Mexico, contain predominantly reverse polarity characteristic magnetizations of high coercivity and distributed unblocking temperature up to 695°C. Data from a syndepositional structure suggest acquisition of a stable remanence during or soon after deposition. The mean paleomagnetic pole for 13 virtual geomagnetic poles (VGP) accepted (of 17 sites collected) is located at 55.2°N, 87.5°E (A95 = 6.7°, K = 39.7). The angular distance between this pole and the mean of recently published middle and late Norian (∼210 Ma) poles from overlying strata is 12.5°, supporting the hypothesis that significant apparent polar wander occurred during Late Triassic time. Furthermore, the Bluewater Creek pole lies to the west (6.1°, angular distance) of the cratonic reference pole for Carnian time supporting the hypothesis of a small Colorado Plateau rotation since the early Mesozoic. Anisian strata of the Moenkopi Formation contain dual polarity magnetizations of high coercivity and distributed unblocking temperatures up to 690°C, The mean VGP of six sites yields is located at 53.1°N, 96.3°E (A95 = 6.4°, K = 109.2), which is similar to previously determined Middle Triassic poles. Triassic paleomagnetic poles from southwest North America from strata in continuous stratigraphic succession, both on and off the Colorado Plateau, are not consistent with the hypothesis of a Late Triassic stand still of the geomagnetic pole.