Permian Paleomagnetism of Eastern Kazakhstan: Implications Concerning the Amalgamation of Eurasia

Kazakhstan is the central and most complex region of the Ural-Mongol belt of Eurasia. This region is bounded by the Baltica platform to the west, the Siberian platform to the northeast, and Tarim to the south. Many geologists think that the major tectonic units of Kazakhstan had amalgamated by the Silurian, with the possibility of relatively small motions through the middle-late Paleozoic, whereas others have postponed the welding of Kazakhstan until the Late Carboniferous. Furthermore, some authors have suggested that the Siberian block and the adjacent regions of the Ural-Mongol belt were displaced with respect to Baltica, westward and northwestward (in present day co-ordinates) during the Late Permian along strike slip faults by some 1500km. We studied Upper Permian volcanics from eastern Kazakhstan (47.5N, 80.5E). A univectorial characteristic remanent magnetization (ChRM) component was isolated from most samples after the removal of a weak, low-temperature remanence. The fold test (McFadden and Jones, 1981) is positive. The observed pole (PLat: 43, Plong: 172, a95: 3.6) falls close to the Baltica APWP and nearly coincides with the mean pole for middle Permian time (261-275 Ma; PLat: 46, Plong: 166, a95: 3.8). The overall agreement of the European and Siberian APWP's is rather good for the Permian, and Late Permian paleolatitudes from Tarim also agree with the European grid. Thus we conclude that our study area had already been attached to the European, Siberian, and Tarim blocks during the Late Permian. This interpretation disagrees with models that suggest large-scale displacement between the European and Siberian platforms during the final stages of Ural-Mongol fold belt evolution.