Paleomagnetic results from the Ordovician Moccasin, bays, and Chapman Ridge Formations of the Valley and Ridge Province, eastern Tennessee

Abstract

New results from the late Early (middle) Ordovician Moccasin, Bays, and Chapman Ridge Formations of the Central Appalachian Mountains indicate that the Early Ordovician was a period of relatively rapid apparent polar wander. The available reliable Late Ordovician poles (Juniata, Beemerville, Trenton) lie in a cluster near 35°N, 120°E separated from the Late Cambrian poles (Wilberns, Lamotte, Wichita Granites) by about 50° of arc. High blocking‐temperature components with positive fold tests from the Moccasin and Bays Formations yield a pole position intermediate between the two clusters at 33°N, 147°E (K = 135, A95 = 5.8°, N=6 sites). High blocking‐temperature components, also with positive fold tests, from the underlying Chapman Ridge Formation give a pole position that agrees well with the Juniata results, and is about 30° from the Moccasin‐Bays pole (27°N, 112°E, K = 38.3, A95 = 15.0°, N = 4 sites). At least two interprettions of these data are possible: (1) the Chapman Ridge Formation acquired its characteristic magnetization during the Late Ordovician or Early Silurian sometime after deposition but before its folding and (2) the path of apparent polar wander with respect to North America described a loop during the Ordovician.