MAGNETOSTRATIGRAPHY OF THE EARLY PERMIAN AND LATE CARBONIFEROUS ROCKS OF THE SOUTHERN KAROO BASIN, SOUTH AFRICA

The Karoo Basin of South Africa experienced marine incursion and thrust loading of the Cape Fold Belt (CFB) during the Permian Period, leading to a localized rapid deepening of the Karoo foreland Basin and restriction of thick clastic sedimentation to the Karoo foredeep. There are controversies surrounding the chronostratigraphy of these sequences, and quite recently, there has been some progress in defining the Permian Triassic Boundary (PTB) in Late Permian rocks and the Kiaman Reverse Superchron (KRS) in the mid to Late Permian rocks of the southern Karoo Basin.

However, the magnetostratigraphic pattern for the Early Permian and Late Carboniferous rocks is not fully located within the southern Karoo Basin. Hence, with the aim of establishing a complete magnetostratigraphic framework for the Permian and Late Carboniferous successions, as well as improving the Early Permian chronostratigraphy of the Karoo Basin, a magnetostratigraphic approach supplemented by rock magnetic records was used in this study.

The rock magnetic and paleomagnetic results agree excellently, showing pyrrhotite and magnetite as the ferromagnetic minerals carrying the Characteristic Remanent Magnetization (ChRM). We present a composite ~ 671 m-thick magnetostratigraphic section that shows a dominantly reversed polarity punctuated by short normal polarity subchrons and correlates with published U-Pb zircon ages and the Geomagnetic Polarity Time Scale (GPTS). We propose magnetostratigraphic ages of ca. 298 – 275 Ma for the Early Permian rocks of the southern Karoo Basin. This, therefore, confirms that deposition of the lower Ecca and Upper Dwyka Group rocks of South Africa occurred during the KRS, and corresponds with the substantial body of worldwide magnetostratigraphic data for Gondwana.