New Proterozoic paleomagnetic data from the Rehoboth Basement Inlier, Namibia, indicating 30-degree clockwise local rotation during Damaran orogenesis.

The Rehoboth Basement Inlier (RBI) lies along the edge of the Kalahari craton at the southern margin of the Pan-African Damara Orogen, Namibia. Knowledge of its location during geologic time will aid future supercontinent reconstructions. Within the RBI, paleomagnetic data were collected from the Bitterwater volcanics and quartzites in the Opdam Formation, the Swartkoppies mafic dykes that presumably feed Opdam basalts, the Uisib River mafic dykes, dolerite dikes intruding the Opdam Formation outside the town of Rehoboth, mafic dykes from the Klein Aub region, and redbeds and volcanics of the Doornpoort Formation. The Bitterwater sites and the Doornpoort Formation sites displayed stable remanent directions, with fold tests indicating the occurrence of syn-folding magnetizations. The shallow inclinations observed in the samples indicate that the folding event occurred prior to the Damara folding event that took place at mid-latitudes, and could be related to a similar syn-folding event observed in the Aubures Formation in the adjacent Konkiep subprovince. The Bitterwater and Doornpoort sites produced two poles estimated to be ca. 1100 Ma in age, although they are rotated 30 degrees clockwise from the well-established ca. 1100 Ma paleopole for the Kalahari craton. One dyke from each of the Swartkoppies and Uisib swarms produced a virtual geomagnetic pole with similar location to those of the Bitterwater and Doornpoort sites. Our results suggest that the Rehoboth Basement Inlier underwent a rotation of approximately 30 degrees clockwise relative to the rest of the Kalahari craton. Previously published data suggest that this rotation affected magnetization as young as ca. 500 Ma. Three Swartkoppies dykes and one Rehoboth dyke produced directions that follow previously compiled Kalahari/Gondwanaland apparent polar wander paths at 1030-1000 Ma and 545-525 Ma, after the 30 degree correction. It is possible that the rotation occurred due to the final closure of an ocean basin between the Congo and Kalahari cratons, although the exact kinematic history will require further study. Our study recognizes the importance of paleomagnetic constraints on supercontinent reconstructions that must take into account regional-scale structural histories.