Paleomagnetism of the Late Ordovician Juniata Formation and the Remagnetization Hypothesis


  • Rob Van der Voo,

  • Rowland B. French


The paleomagnetism of 103 samples from purplish gray sandstones of the Juniata Formation has been investigated. The samples were collected at 17 sites in Virginia, West Virginia, and Pennsylvania. Thermal demagnetization showed a strong magnetic overprinting in a large number of samples. This magnetization is secondary, since it was acquired during or after the late Paleozoic folding of the area; the resulting pole position, at 47°N, 129°E, agrees with published Late Carboniferous to Early Permian pole positions for North America. In all but 12 samples, directions of another component of magnetization could be determined in thermal demagnetization up to 672°C. These are assumed to represent the original magnetization of the Juniata Formation; they were acquired before the folding, and they show both normal and reversed polarities. The resulting pole position, at 31.5°N, 114,4°E (k = 55, α95 = 5°), falls directly in between published Middle Ordovician and Late Silurian pole positions for cratonic North America.