PALEOMAGNETISM AND TECTONICS OF THE SOUTHERN TARIM BASIN, NORTHWESTERN CHINA

We report Late Carboniferous, Permian, and early Tertiary paleomagneti c data from the southern Tarim basin. Prefolding magnetizations were i solated in each case. The Late Carboniferous-Permian and early Tertiar y 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 s everal basins throughout central Asia are similar, yet significantly ( 10 degrees to 20 degrees) shallower than those predicted by the Eurasi an apparent polar wander path. Resolving this discrepancy remains a ma ,;or problem in Asian paleomagnetism. Discordance of the late Paleozoi c poles from Tarim and Siberia suggest that Tarim has rotated about 30 degrees counterclockwise with respect to Siberia since the Permian. W here paleomagnetic samples of both Late Carboniferous to Early Triassi c (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 l ocality. This suggests that (1) only a difference in inclination (and not declination) distinguishes the two data sets, and (2) vertical axi s block rotations of the C3-E1 strata occurred after E1. Although base d 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. T he similarity of all the poles and the analogous tectonic setting of p resent-day central Asia to that of the late Paleozoic in eastern North America raises the question whether all the data from Tarim are overp rinted.