Paleomagnetism and tectonics of the southern Tarim basin, northwestern China

We report Late Carboniferous, Permian, and early Tertiary paleomagnetic data from the southern Tarim basin. Prefolding magnetizations were isolated in each case. The Late Carboniferous-Permian and early Tertiary poles lie at 64.6 degrees N, 166.5 degrees E, A(95)=6.3 degrees and 58.1 degrees N, 202.0 degrees E, A(95)=12.7 degrees, respectively. The Late Jurassic to early Tertiary (J3-E1) paleolatitudes of Tarim and several basins throughout central Asia are similar, yet significantly (10 degrees to 20 degrees) shallower than those predicted by the Eurasian apparent polar wander path. Resolving this discrepancy remains a ma,;or problem in Asian paleomagnetism. Discordance of the late Paleozoic poles from Tarim and Siberia suggest that Tarim has rotated about 30 degrees counterclockwise with respect to Siberia since the Permian. Where paleomagnetic samples of both Late Carboniferous to Early Triassic (C3-T1) and J3-E1 ages were collected from the same area of Tarim, a great circle passes through the means of the poles and the sampling locality. This suggests that (1) only a difference in inclination (and not declination) distinguishes the two data sets, and (2) vertical axis block rotations of the C3-E1 strata occurred after E1. Although based on data of lesser quality, the mean Early to Middle Jurassic (J1-2) pole from Tarim differs significantly from the Eurasian reference pole, requiring radical tectonic solutions to resolve them. The Tarim J1-2 pole is indistinguishable from both the mean J3-E1 and C3-T1 poles. The similarity of all the poles and the analogous tectonic setting of present-day central Asia to that of the late Paleozoic in eastern North America raises the question whether all the data from Tarim are overprinted.