A paleomagnetic study of Triassic sedimentary rocks from Qinshui Basin, Shanxi Province, North China

The results of a combined paleomagnetic, rock magnetic and petrographic study of Middle and Lower Triassic from Qinshui Basin, North China Block are reported. The characteristic remanent magnetization from the Ermaying Formation (Middle Triassic) is carried by both magnetite and hematite. In stratigraphic coordinates, the direction (Dec. = -28 degrees, Inc. = 44 degrees, N = 10, alpha(95) = 4 degrees) passes the (incremental) fold test and fabric test. The corresponding paleopole is 64 degrees N, 6 degrees E. The remanent magnetization of samples from the bottom of the Liujiagou Formation (Lower Triassic) is carried mainly by magnetite, which shows an inverse magnetic fabric and an abnormal magnetization direction. This is probably caused by a bedding-parallel compression. A comparison of Triassic paleopoles from this locality with others in North China reveals a significant tectonic rotation of the eastern North China Block and Korean Peninsula with respect to the western North China Block. The rotation probably occurred during the Indosinian Movement.