A geomagnetic polarity timescale for the Permian, calibrated to stage boundaries

Abstract

© 2018 The Author(s). The reverse polarity Kiaman Superchron has strong evidence for at least three, or probably four, normal magnetochrons during the early Permian. Normal magnetochrons are during the early Asselian (base CI1r.1n at 297.94±0.33 Ma), late Artinskian (CI2n at 281.24±2.3 Ma), mid-Kungurian (CI3n at 275.86±2.0 Ma) and Roa"dian (CI3r.an at 269.54±1.6 Ma). The mixed-polarity Illawarra Superchron begins in the early Wordian at 266.66±0.76 Ma. The Wordian- Capitanian interval is biased to normal polarity, but the basal Wuchiapingian begins the beginning of a significant reverse polarity magnetochron LP0r, with an overlying mixed-polarity interval through the later Lopingian. No significant magnetostratigraphic data gaps exist in the Permian geomagnetic polarity record. The early Cisuralian magnetochrons are calibrated to a succession of fusulinid zones, the later Cisuralian and Guadalupian to a conodont and fusulinid biostratigraphy, and Lopingian magnetochrons to conodont zonations. Age calibration of the magnetochrons is obtained through a Bayesian approach using 35 radiometric dates, and 95% confidence intervals on the ages and chron durations are obtained. The dating control points are most numerous in the Gzhelian-Asselian, Wordian and Changhsingian intervals. This significant advance should provide a framework for better correlation and dating of the marine and non-marine Permian.