PALEOMAGNETISM OF PERMIAN SEDIMENTARY-ROCKS FROM TANZANIA AND THE PERMIAN PALEOGEOGRAPHY OF PANGEA

We report new paleomagnetic results from Karoo (Permian) rocks in Tanz ania. K1 and K3 redbeds and K5 siltstones and limestones from the Song we-Kiwira Basin, Ndeke redbeds from the Mikumi Basin, and group VIII r edbeds from the Nyakatitu Basin were sampled and thermally demagnetize d. Palynologic data and lithologic correlations suggest that the K1 re dbeds are Lower Permian, and that the K3, Ndeke, and group VIII redbed s, as well as the K5 siltstones and limestones, are Upper Permian. Sta ble magnetic directions were obtained from the K3, Ndeke, and group VI II redbeds, yielding an Upper Permian pole at 26-degrees-N, 267-degree s-E. Characteristic remanence directions were also obtained from the K 5 siltstones and limestones. However, because these directions define a pole (66-degrees-N, 269-degrees-E) that is very close to the Upper C retaceous pole for Africa and significantly different from the Upper P ermian redbed poles, these rocks may have been remagnetized. The K1 re dbeds did not yield stable results. Using our new results together wit h published Permian poles for Africa and the other Gondwanan continent s, we revise the mean Lower and Upper Permian poles for Africa, West G ondwana, and Gondwana, and investigate whether or not these revised po les can discriminate between the various Pangea reconstructions propos ed for the Permian with any greater certainty than previous (unrevised ) mean poles. When compared to the mean Lower and Upper Permian poles for Laurussia, we find that our revised West Gondwanan and Gondwanan p oles do not necessarily provide stronger support for any particular Pa ngea reconstruction than the previous poles. Therefore, even though th is study improves the paleomagnetic data base for Gondwana for the Per mian, it is not clear that the combination of our results with other p aleomagnetic data from the Gondwanan continents yields significant new insights about the Permian configuration of Pangea. As suggested prev iously, strong non-dipole fields during the Permian may provide an exp lanation for why it is not easy to discriminate with certainty between the various Permian Pangea reconstructions, even with new paleomagnet ic results.