Permian Magnetostratigraphy and End of the Kiaman Reverse Polarity Superchron From the Southeast Karoo Basin, South Africa

Abstract

Paleomagnetic results for a ∼2,353-m-thick magnetostratigraphic section for undeformed middle to late Permian rocks in the southeast of the Karoo Basin of South Africa are reported. Predominantly pseudo-single-domain or single-domain titanomagnetite (with possible minor contributions by pyrrhotite and multi-domain magnetite) were identified as remanence carriers of a dual polarity magnetization interpreted as the record of the Permian geomagnetic field during the Kiaman Reverse Polarity Superchron and subsequent Illawarra mixed polarity interval. The timing of remanence acquisition is further constrained by the effect of Jurassic-aged dolerite intrusions, which either partially or wholly overprint the Permian remanence in their immediate vicinity. A paleopole at 62.0°S; 64.3°E and dp/dm = 4.9°/5.8° is calculated from the bedding-corrected primary remanence (when corrected for inclination shallowing at f = 0.6 the paleopole is located at 53.2°S; 46.9°E and dp/dm = 5.9°/6.3°). This is comparable to other Permian paleopoles from the southwest section of the Karoo Basin. The end of the Kiaman Reverse Polarity Superchron can be correlated between the E-W extremes of the basin to reveal a diachronous boundary between the Ecca and the Beaufort groups, with diachronicity calibrated to 1.1 million years for the first time.