Palaeomagnetism of the permo/carboniferous (280 Ma) Jebel Nehoud ring complex, Kordofan, Central Sudan

Abstract

Palaeogeographic reconstructions of Pangaea during Permian times, based on palaeomagnetic data, result in major overlaps between Gondwana and Laurasia when choosing a Wegener type configuration (Pangaea A1 or A2). In order to reduce these overlaps, several alternative reconstructions for Pangaea have been proposed whereby Gondwana is shifted towards the east with respect to Laurasia (Pangaea B and Pangaea C). Although these configurations are perfectly compatible with the palaeomagnetic data set, they are not accepted by the majority of the earth science community. Gondwana's palaeomagnetic data set is of rather low quality and often hampered by large uncertainties in rock age. The overlap of Laurasia and Gondwana, therefore, may be an artefact. Here we present new palaeomagnetic data for the radiometrically dated (280±2 Ma, single mineral, K–Ar) Jebel Nehoud ring complex, Northern Kordofan, Sudan. The majority of the samples studied show rather simple directional behavior. After removal of component A, pointing to the north with shallow inclinations and bearing great similarity to the direction of the present day Earth's magnetic field in the region, component B was identified at demagnetization temperatures above 380 °C. Maximum unblocking temperatures for component B reach 580 °C and only occasionally 650 °C or higher, suggesting magnetite and occasionally haematite as the principal carriers of component B. Component B is of single polarity and points towards the southeast with intermediate inclinations. The resulting overall mean south pole position based on eight sites is 40.8°S and 71.3°E ( k: 78.1; α 95: 6.0) and 46.5°S; 68.0°E when transferred into northwest African coordinates. Combining this new pole position with the highest quality data from Australia, South America and Africa results in a mean pole position at 37.3°S; 63.8°E ( N=11, k=84.5, α 95=5.0) in northwest African coordinates and removes some of the ambiguities in the Gondwana data set for the Early Permian. However, the palaeogeographic reconstruction of Gondwana on the basis of the new data, results in a major overlap with Laurasia when a Pangaea A2 configuration is chosen, whilst it is fully compatible with a Pangaea B type configuration.