Kiaman Magnetic Interval in the Western United States

Abstract

Late-Paleozoic red beds in the western United States indicate that Earth's magnetic field was reversed for a period of the order of 50 x 10⁶ years. This finding agrees with similar results from igneous rocks in Australia, indicating, that the long period of reversal in the magnetic field was worldwide. The rocks on the two continents appear to be essentially equivalent in time, suggesting early magnetization of the red beds. The time spectrum of reversals is irregular in geologic time, but present evidence suggests reversals characterized by time scales of 10⁴ or 10⁵, 10⁶, and 50 x 10⁶ years. The 50 x 10⁶ year period of steady reversed field is found in the late Paleozoic and is termed the Kiaman magnetic interval.