Late Paleozoic Partial Remagnetization of Ordovician Rocks from Southern Oklahoma
Measurements of the NRM (natural remanent magnetization) of Lower Ordovician sediments collected from both flanks of the Arbuckle anticline (south-central Oklahoma) correspond to an upper Carboniferous–Permian magnetization direction. Directions of magnetization are well grouped and remain essentially unchanged through thermal demagnetizations up to 400°C. Correction for folding indicates that the magnetization is post-folding and that the Arbuckle orogeny was of sufficient intensity to heat and remagnetize the sediments involved. Upon thermal demagnetization to temperatures of 550°C, the directions of magnetization changed considerably to directions distinctly removed from the observed upper Carboniferous–Permian direction. Sample in-in tensities are very weak and therefore a reliable direction was unattainable. The data form a streaked distribution away from the Carboniferous-Permian direction. The calculated upper Carboniferous–Permian pole, corrected for the primary prefolding remanence direction observed above 400°C, is located at 128.9° E., 46.1° N. Orogenic temperature calculations based on differing stabilities of this late Paleozoic remanence on opposite flanks of the anticline indicate a more intense orogeny to the north with minimum temperatures of 200°C. Lesser temperatures, of at least 120°C but less than 200°C, prevailed on the south flank.