A Lower Ordovician paleomagnetic pole from the Oneota dolomite, upper Mississippi River Valley ( USA).

Of 149 oriented specimens of the lower Ordovician Oneota dolomite subjected to stepwise thermal or alternating-field demagnetization, 50 contained a characteristic shallow ESE or WNW component of magnetization. For 48 other specimens the demagnetization trajectories defined great-circle paths which intersect close to the characteristic direction. The site-mean directions for the characteristic component were determined by using both the characteristic directions and great-circle data, and these yield a formation-mean direction obtained from 10 sites with a declination of 105o, an inclination of +2o, and a precision parameter k of 17.6 (alpha 95 = 11.9o). The mean of the site virtual poles falls at 10.4o N, 166.4o E (K = 48.0, A95 = 7.0o), which is close to previously published late Cambrian paleopoles. It is suggested that the stable remanence in the Oneota dolomite was acquired prior to the deposition of the New Richmond sandstone.-after Authors