Palaeomagnetic and geochronological data from Late Mesoproterozoic redbed sedimentary rocks on the western margin of Kalahari craton

Abstract

Abstract Redbeds of the Aubures Formation constitute the uppermost stratigraphic unit in the Mesoproterozoic Sinclair succession of southern Namibia. Aubures palaeomagnetic remanence vectors, held almost exclusively by hematite, document at least one geomagnetic polarity reversal in the stratigraphy, a positive intraformational conglomerate test indicating primary magnetization and greatest concentration of characteristic directions at 50–60% untilting, indicating that deformation was coincident with sedimentation. The new Aubures palaeomagnetic pole, at 56.4°N and 018.0°E with A 95 =11.3°, is located on the apparent polar wander path of the Kalahari craton, between poles of the 1110 Ma Umkondo igneous event and the c. 1090 Ma Kalkpunt redbeds of the Koras Group near Upington, South Africa. This distinctive concordance suggests that Aubures sediments have an age of approximately 1100 Ma, that the Sinclair region was probably part of Kalahari at that time and that the Aubures and Kalkpunt redbeds are broadly correlative. New laser-ablation inductively coupled plasma mass spectrometry detrital zircon results from the Aubures Formation, including a youngest age component (1108±9 Ma) that is coincident with the Kalahari-wide Umkondo large igneous province, conform to this interpretation. Palaeomagnetism and geochronology of the Sinclair succession can provide kinematic constraints on the tectonic evolution of Kalahari as it approached other cratons in the growing Rodinia supercontinent.