PRELIMINARY EARLY CRETACEOUS PALEOMAGNETIC RESULTS FROM THE GANSU CORRIDOR, CHINA

We report results from our paleomagnetic study of Lower Cretaceous red beds from the Gansu Corridor, northwestern China. The characteristic r emanent magnetization (ChRM) resides in hematite, often at very high u nblocking temperatures (> 660 degrees C). The directions associated wi th this component exhibit only reversed polarities from locality A (Su nan area), but the samples from locality B (Lanzhou area, 480 km to th e southeast) show roughly antipodal normal and reversed polarities. Th e combined sample directional data from both localities pass a fold te st at the 99% confidence level. The mean paleomagnetic pole is located at 48.7 degrees N, 199.7 degrees E, with A(95) = 4.1 degrees, which i s discordant with poles of similar age elsewhere from neighboring regi ons in China. Although represented by relatively few samples (N = 21) this pole suggests that significant post-Cretaceous motion may have oc curred between the Gansu Corridor and adjacent blocks. Relative to Eur asia or North China, the discordance corresponds to 28.1 +/- 5.2 degre es or 35.6 degrees +/- 9.7 degrees clockwise rotation and 9.5 degrees +/- 4.5 degrees or 9.8 degrees +/- 8.2 degrees northward displacement respectively. The rotations support, but do not yet distinguish betwee n, several neotectonic models assumed to have acted over the past 15-4 0 m.y. The displacement is not predicted by any of these models; if re al, it may have occurred early in the history of the India-Asia collis ion, or even before.