THE STATIONARY CRETACEOUS PALEOMAGNETIC POLE OF SICHUAN (SOUTH CHINA BLOCK)

Upper Jurassic to lower Tertiary sites have been sampled from three localities, separated by up to 150 km, in the Sichuan Basin (approximately 30-degrees-N, 103-degrees-E) of the South China Block. Each locality has at least one stability test, but none alone gives a fully reliable result. When taken together, however, identical directions are found with a global average D = 12.7-degrees, I = 34.2-degrees, k = 42.9-degrees, alpha-95 = 3.3-degrees (N = 44 sites) and corresponding pole 73.9-degrees-N, 234.4-degrees-E, dp = 2.2-degrees, dm = 3.8-degrees, paleolatitude lambda = 18.8-degrees. There is no significant apparent polar wander (APW) with age, which is consistent with an acquisition of magnetization during the period of the stable tip of the Eurasian APW loop (approximately 130-70 Ma), as defined with poles from other continents transferred onto Eurasia. This age range is compatible with the available paleontological and magnetostratigraphic age constraints but is shorter than that suggested by the assigned formation ages. The paleolatitude of Sichuan is significantly lower (8.0-degrees +/- 4.0-degrees at 90 Ma) than that predicted by the reference APW path, either because of northward shortening during the Tertiary or because of errors in the APW path. Cretaceous poles from other Chinese blocks are consistent with the Sichuan pole, but there is evidence that these blocks have suffered local rotations up to 10-degrees during the Tertiary, probably as a result of the India-Eurasia collision.