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

Abstract

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.

Refining the chronostratigraphy of the Karoo Basin, South Africa: magnetostratigraphic constraints support an early Permian age for the Ecca Group

“…The magnetostratigraphy shows an extended reverse polarity interval for over 1500 m of section that is consistent with formation during the Pennsylvanian-Middle Permian KRS (Hounslow and Balabanov, 2016;Irving and Parry, 1963;Menning et al, 1988;Opdyke et al, 2000;Steiner, 2006). This interval of constant magnetic polarity was followed by a return to a frequently reversing field at ca.…”

“…The reversal stratigraphy (declination, inclination, and VGP Latitude) was then plotted against sampling level and a composite magnetostratigraphic barcode was completed and compared with the GPTS (Hounslow and Balabanov, 2016;Ogg et al, 2016). Magnetic reversals were interpreted from remanence directions that crossed the magnetic equator (defined as 90° along a great circle from the mean direction) where three or more consecutive samples define a magnetozone.…”

“…7d), and may be correlative with previously documented ca. 275 Ma normal subchrons within the KRS (Hounslow and Balabanov, 2016).…”

Aridification across the Carboniferous–Permian transition in central equatorial Pangea: The Catalan Pyrenean succession (NE Iberian Peninsula)

“…Given the long expanded interval of reverse polarity and the biostratigraphic constraints and absolute ages (see below), we directly correlate it to the Kiaman reverse Superchron (Hounslow and Balabanov, 2016). In the most recent Permian polarity timescale, the Kiaman Superchron extends up to the mid Guadalupian Epoch (or early Wordian stage) at about 266 Ma (Hounslow and Balabanov, 2016) where the mixed Illawarra Superchron begins. This implies that the studied LRU section is no younger than earliest middle Permian.…”

Paleomagnetic Secular Variation Constraints on the Rapid Eruption of the Emeishan Continental Flood Basalts in Southwestern China and Northern Vietnam

“…A magnetostratigraphic study of the ELIP can potentially yield valuable information about the duration of the emplacement and the eruption rates. Although the thick sequence of the ELIP is well known for containing two geomagnetic polarity zones, as proposed by Zheng et al (), and previous magnetostratigraphic results (Ali et al, ; K. N. Huang & Opdyke, ; Liu et al, ; Zheng et al, ) favor a model of rapid emplacement with a duration of 1–3 Myr, the geomagnetic polarity timescale spanning the Middle‐Late Permian remains controversial (Hounslow & Balabanov, ; Ogg & Hinnov, ). In addition, the uncertainties involved in radiometric dating are too large to constrain the short duration of the Emeishan eruption.…”