Paleomagnetic results of the Late Permian Gobangsan Formation, Korean Peninsula: Remagnetization in the southeastern periphery of the Bagjisan Syncline

Sedimentary rocks in the Late Permian Gobangsan Formation were collected at 7 sites for paleomagnetic study in the southeastern periphery of the Bagji san Syncline, Korean Peninsula. The Gobangsan Formation revealed a stable s econdary magnetization component with unblocking temperatures of 500-580 de grees C and 650 degrees C from two sites, while the other sites possessed o nly a present day viscous remanence. The secondary component resides in mag netite and hematite. The site-mean directions of the two sites before tilt correction (D = 355.9 degrees, I = 50.2 degrees with alpha(95) = 4.3 degree s and D = 355.7 degrees, I = 53.3 degrees with alpha(95) = 6.1 degrees) sug gest that the remagnetization occurred after Early Cretaceous. The most pla usible mechanism of the remagnetization is considered to be a chemical auth igenesis because the other possible mechanisms of the remagnetization such as thermoviscous process and Recent weathering can be ruled out by rock mag netic experiments. The timing of the remagnetization is constrained during Tertiary time, because the observed directions are distinguishable from the Cretaceous directions and because Recent remagnetization is unlikely. This is ascertained by good agreement between the observed and the Tertiary dir ections.