HR: 0800h
AN: GP21A-0101    [Abstracts]
TI: Late Cretaceous-Early Tertiary remagnetization recorded on sedimentary rocks in the Jinan Basin, Korea
AU: * Lee, J
EM: hnst@korea.ac.kr
AF: Department of Earth and Environmental Sciences, Korea University, Seoul, 136-713, Korea, Republic of
AU: Doh, S
EM: sjdoh@korea.ac.kr
AF: Department of Earth and Environmental Sciences, Korea University, Seoul, 136-713, Korea, Republic of
AU: Kim, W
EM: wnkim@korea.ac.kr
AF: Department of Earth and Environmental Sciences, Korea University, Seoul, 136-713, Korea, Republic of
AU: Yu, Y
EM: yongjaeyu@korea.ac.kr
AF: Department of Earth and Environmental Sciences, Korea University, Seoul, 136-713, Korea, Republic of
AU: Suk, D
EM: dwsuk@hanyang.ac.kr
AF: Department of Environmental Marine Sciences, Hanyang University, Ansan, 425-791, Korea, Republic of
AB: In order to decipher the tectonic evolution of the Korean Peninsula, a paleomagnetic study has been carried out for the Cretaceous rocks in the Jinan Basin, southwestern part of the Ogcheon Metamorphic Belt (OMB), Korea. Demagnetization of 1089 independently oriented specimens successfully isolated characteristic remanent magnetization (ChRM) as a secondary overprint. A suite of rock magnetic experiments revealed that fine-grained hematite, magnetite and/or pyrrhotite are remanence carriers. Two distinctively different paleomagnetic poles were obtained: 111.8°E and 87.9°N ( A₉₅ = 3.5°) for Dalgil and Sansudong formations; and 181.7°E and 80.5°N ( A₉₅ = 3.1°) for Mandeoksan Formation. These pole positions lie fairly close to the Late Cretaceous and Tertiary pole, respectively, indicating a back-to-back remagnetization in Late Cretaceous and in Early Tertiary. During this period, igneous activities (Bulguksa Disturbance) had been pervasive throughout the Korean Peninsula due to a change in subduction-regime of the Kula-Pacific plate. As in previously reported sedimentary rocks in the OMB, ChRMs are overprinted by authigenically formed hematite that precipitated from iron-bearing hydrothermal fluids. It is likely that authigenic hematite had been formed during the early stage of igneous activity. On locking of Late Cretaceous paleofields by secondary hematite, the steady heat from the igneous body possibly generated secondary pyrrhotite and magnetite by consuming pyrite and abundant organic materials.
DE: 1500 GEOMAGNETISM AND PALEOMAGNETISM
DE: 1525 Paleomagnetism applied to tectonics: regional, global
DE: 1527 Paleomagnetism applied to geologic processes
DE: 1533 Remagnetization
DE: 1540 Rock and mineral magnetism
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting