Clockwise rotation of the Korean Peninsula with respect to the North ChinaBlock inferred from an improved Early Triassic palaeomagnetic pole for theRyeongnam Block

In order to detect a possible clockwise rotation of the Korean Peninsula wi th respect to the North China Block, Early Triassic rocks in the Ryeongnam Block, Korean Peninsula have been restudied. Sandstones in the Nogam Format ion were collected at four sites for palaeomagnetic study. A high-temperatu re magnetization component with an unblocking temperature of 690 degreesC i s isolated from all sites and yields a positive fold test at the 95 per cen t confidence level. This high-temperature component is interpreted to be of primary origin because folding is Middle Triassic in age. The primary dire ctions together with previously reported ones give a new Early Triassic mea n direction (D = 347.4 degrees, I = 23.8 degrees, alpha (95) = 5.1 degrees) and corresponding palaeomagnetic pole (62.6 degreesN, 336.1 degreesE, A(95 ) = 4.2 degrees) for the Ryeongnam Block. This improved Early Triassic pole for the Ryeongnam Block is located to the west of the coeval poles for the North China Block. It is therefore concluded that the Ryeongnam Block unde rwent clockwise rotation of 10 degrees -15 degrees with respect to the Nort h China Block. Because the amount of rotation observed in the present study is comparable with rotations observed in Cretaceous results from the Ryeon gnam Block and in the Triassic-Cretaceous results from other blocks in the Korean Peninsula, the whole of the Korean Peninsula appears to have been su bjected to clockwise rotation in Tertiary times.