PALEOMAGNETISM OF EOCENE VOLCANIC-ROCKS, TALKEETNA MOUNTAINS, ALASKA

Tests an alternative hypothesis used to explain palaeolatitude variations between the north and south of the southern Alaska superterrane, based on a postulated unrecognized tectonic boundary separating the two localities, allowing different emplacement ages. Assuming Eocene emplacement of the SAS, Eocene volcanic rocks deposited near the southern edge of the SAS in the Talkeetna Mountains were sampled. Results rule out the hypothesis of an unrecognized suture accommodating major post-Eocene displacement. Reevaluation of the data suggest rapid movement, including the precision of the age control, the adequacy of averaging of secular variation, and the possibility of sedimentary inclination error. The bulk of the evidence suggests northward displacement from lower latitudes; however, the error limits are such that the dramatic velocities previously postulated are not required. -after Authors