Magnetic Characterization of the Cretaceous Rocks from the Buyeo and Hampyeong Basins

부여분지와 함평분지에 분포하는 백악기 암석에 대한 자기특성 연구

  • Hong, Jun-Pyo (Dept. of Environmental Marine Sciences, Hanyang Univ.) ;
  • Suk, Dong-Woo (Dept. of Environmental Marine Sciences, Hanyang Univ.) ;
  • Doh, Seong-Jae (Dept. of Earth and Environmental Sciences, Korea Univ.)
  • 홍준표 (한양대학교 해양환경과학과) ;
  • 석동우 (한양대학교 해양환경과학과) ;
  • 도성재 (고려대학교 지구환경과학과)
  • Published : 2007.04.28

Abstract

A paleomagnetic investigation for the Cretaceous rocks in the Buyeo and Hampyeong Basins, located out of the Gyeongsang Basin, was carried out in order to elucidate the paleomagnetic directions in conjunction with the formation of the basins. Typical stepwise thermal demagnetization and measurement methods were used to determine the directions of characteristic remanent magnetizations (ChRMs). The mean direction of the sedimentary rocks from the Buyeo Basin after bedding correction $(D/I=356.5^{\circ}/61.5^{\circ},\;k=39.3\;\alpha_{95}=7.4^{\circ})$, is more dispersed than that before bedding correction $(D/I=356.5^{\circ}/61.5^{\circ},\;k=39.3\;\alpha_{95}=7.4^{\circ})$, which suggests that the rocks in the Buyeo Basin were remagnetized. However, the statistics and dispersion of the ChRM directions after bedding correction are still acceptable and the paleomagnetic pole position after tilt correction $(Lat./Long.=69.3^{\circ}N/186.7^{\circ}E,\;K=11.6\;A_{95}=14.0^{\circ})$ is closer to that of the Late Cretaceous pole of the Korean Peninsula. More detailed study is needed to confirm the nature of the remagnetization in the Buyeo Basin. On the other hand, the paleomagnetic pole before bedding correction $(Lat./Long.=81.6^{\circ}N/106.9^{\circ}E,\;K=25.1\;A_{95}=9.3^{\circ})$ is positioned near the paleogene pole of the Eurasian APWP. The mean ChRM direction of the sedimentary rocks from the Hampyeong Basin after bedding correction is $D/I=32.5^{\circ}/55.4^{\circ},\;(k=35.6,\;\alpha_{95}=8.7^{\circ})$. It is more clustered than that before bedding correction $D/I=18.3^{\circ}/62.5^{\circ},\;k=14.1,\;\alpha_{95}=14.2^{\circ})$, indicating that the ChRM was acquired before tilting of the strata. The paleomagnetic pole position of the Cretaceous sedimentary rocks in the Hampyeong Basin, averaged out of site pole positions calculated from the tilt-corrected ChRMs, is $Lat./Long.=63.9^{\circ}N/202.7^{\circ}E,\;(K=21.3,\;A_{95}=7.6^{\circ})$, similar to the Late Cretaceous paleomagnetic pole of the Korean Peninsula $(Lat./Long.=70.9^{\circ}N/215.4^{\circ}E,\;A_{95}=5.3^{\circ})$, suggesting that the Hampyeong Basin has been stable since the Late Cretaceous period. One normal and two reversed ChRM directions are revealed through the measurements of the volcanic rocks from the Hampyeong Basin. Although these normal and reversed directions are not exactly antipodal, it is interpreted that the normal direction is the representative primary direction of the volcanic rocks of the Hampyeong Basin and the mixed polarity is the records of geomagnetic field at the time of the formation of the volcanic rocks. Paleomagnetic poles are at $Lat./Long.=70.2^{\circ}N/199.5^{\circ}E,\;(K=18.1,\;A_{95}=9.6^{\circ})$ for the normal direction, and $Lat./Long.=65.5^{\circ}S/251.3^{\circ}E,\;(K=7.1,\;A_{95}=20.7^{\circ})$ for the reversed direction. Compared with the representative pole positions of the Cretaceous period of the Korean Peninsula, it is concluded that the age of the volcanic rocks in the Hampyeong Basin is of the Late Cretaceous.

References

  1. Besse, J. and Courtillot, V. (1991) Revised and synthetic polar wander paths of the African, Eurasian, North American and Indian plates, and true polar wander since 200 Ma. Jour. Geophys. Res., v.96, p.4029-4050 https://doi.org/10.1029/90JB01916
  2. Chang, K. H. (1975) Cretaceous stratigraphy of southeast Korea. Jour. Geol. Soc. Korea, v.11, p.1-23
  3. Choi, Y.S. (1996) Structural evolution of the Cretaceous Eumseong Basin, Korea. Ph.D. thesis, Seoul National Univ., 158p
  4. Chun, S. S. (1989) Sedimentary processes, depositional environments, and tectonic settings of the Cretaceous Uhangri Formation, Southwest Korea. Ph.D. thesis, Seoul National Univ., 328p
  5. Chun, S.S. and Chough, S.K. (1992) Tectonic history of Cretaceous sedimentary basins in the southwestern Korean Peninsula and Yellow Sea. In Chough, S.K (ed.) Sedimentary basins in the Korean Peninsula and adjacent seas. Hanlim Pub., Seoul, p.60-76
  6. Chun, H.Y., Choi, Y.S., Choi, S.J., Kim, Y.B., Kim, B.C., Lee, B.S. and Bong, P.Y. (1994) Fossil floral and faunal assemblages and paleoenvironmental modelling study on the Cretaceous sedimentary basins scattered in/ near the Ogcheon belt(). KR-94(T)-11, KIGAM, 101p
  7. Doh, S.J., Hwang, C.S. and Kim, K.H., (1994) A palaeomagnetic study of sedimentary rocks from Gyeongsang Supergroup in Milyang Sub-Basin. Jour. Geol. Soc. Korea, v.30, p.211-228
  8. Doh, S.J., Cho, Y.Y. and Suk, D. (1996) Remagnetization of the Cretaceous sedimentary rocks in the Yeongdong Basin. Econ. Environ, Geol., v.29, p.193-206
  9. Doh, S.J., Suk, D. and Kim, B.C. (1999a) Paleomagnetism of the Cretaceous sedimentary rocks in the Yeongyang Sub-Basin. Econ. Environ. Geol. v.32, p.189-201
  10. Doh, S.J., Suk, D. and Kim, B.Y. (1999b) Paleomagnetic and rock-magnetic studies of Cretaceous rocks in the Eumseong Basin, Korea. Earth Planets Space, v.51, p.337-349 https://doi.org/10.1186/BF03352238
  11. Doh, S-J., Kim, W., Suk, D., Park, Y-H. and Cheong, D. (2002) Paleomagnetic and rock-magnetic studies of Cretaceous rocks in the Gongju Basin, Korea: Implication of clockwise rotation. Geophys. J. Int., v.150, p.737-752 https://doi.org/10.1046/j.1365-246X.2002.01726.x
  12. Fisher, R.A. (1953) Dispersion on a sphere. Proc. R. Soc. London, A217, p.295-305
  13. Geological Society of Korea (1999) The geology of Korea. Sigma Press, Seoul, 802p
  14. Hwang, J.H., Kim, B.C., Kee, W.S., Song, G.Y. and Lee, S.R. (2002) Geological report of the Ham-Pyeong sheet (1:25,000). KIGAM, 58p
  15. Jung, S.W. (1987) A structural study of the northern part of a Cretaceous basin in Jeungpyeong-Eumseong area. M.S. thesis, Seoul National Univ., 68p
  16. Kim, B. C. (1996) Sequential development of depositional systems in a strike-slip basin: Southern part of the Cretaceous Yongdong basin, Korea. Ph.D. thesis, Yonsei Univ., 336p
  17. Kim, K.H. and Noh, B.S. (1993) Palaeomagnetic study of the Cretaceous rocks in the Okchon Belt: Palaeomagnetism of the sedimentary rocks in the Neungju Basin. Jour. Korean Earth Sci. Soc. v.14, p.44-57
  18. Kim, I.S., Lee, H.K., Yun, H.S. and Kang, H.C. (1993) Paleomagnetism of Cretaceous rocks in the Uiseong area, Kyongsang basin, Korea. Jour. Korea Inst. Mining Geol., v.26, p.403-420
  19. Kim, J.H., Lee, J.Y. and Kee, W.S. (1994) Structural evolution of the Cretaceous Puyeo Basin, Korea. Jour. Geol. Soc. Korea, v.30, p.182-192
  20. Kirschvink, J.L. (1980) The least squares line and plane and the analysis of paleomagnetic data. Geophys. J. R. Astron. Soc., v.62, p.669-718
  21. Lee, H.G (1986) Structural analysis of the Gong-ju pull-apart Basin, Korea. M.S.. thesis, Seoul National Univ., 80p
  22. Lee, J.Y. (1990) Structural evolution of the Gongju Basin. Ph.D. thesis, Seoul National Univ., 219p
  23. Lee, Y.Y. (1992) Stratigraphy, depositional environments, and evolution of the Cretaceous Chinan Basin. Ph.D. thesis, Seoul National Univ., 287p
  24. Lee, D.W. and Paik, K.H. (1990) Evolution of strike-slip fault controlled Cretaceous Yongdong Basin, South Korea: Signs of strike-slip tectonics during infilling. Jour. Geol. Soc. Korea, 26, p.257-276
  25. Lim, M.T., Lee, Y.S., Kang, H.C., Kim, J.Y. and Park, I.H. (2001) Paleomagnetic study on Cretaceous rocks in Haenam area. Econ. Environ. Geol., v.34, p.119-131
  26. McFadden, P.L. and McElhinny, M.W. (1988) The combined analysis of remagnetization circles and direct observations in palaeomagnetism. Earth Planet. Sci. Lett., v.87, p.161-172 https://doi.org/10.1016/0012-821X(88)90072-6
  27. Park, Y.H. and Doh, S.J., (2004) Paleomagnetic and rockmagnetic studies of the Cretaceous sedimentary rocks in the Poongam Basin. Econ. Environ. Geol. v.37, p.195-206
  28. Park, Y.H., Doh, S.J., Ryu, I.C., and Suk, D. (2005) A synthesis of Cretaceous palaeomagnetic data from South Korea: Tectonic implications in East Asia. Geophys. Jour. Int., v.162, p.709-724 https://doi.org/10.1111/j.1365-246X.2005.02584.x
  29. Shimamura, S. (1931) Geological report of the Buyeo sheet (1:50,000), Geological Survey of Joseon
  30. Suk, D. and Doh, S.J. (1996) Palaeomagnetism of the Cretaceous rocks in Euiseong area Revisited. Jour. Geol. Soc. Korea, v.32, p.47-64
  31. You, H.S., Paul K., Koh, Y.K., Yun, S.T., Kim, J.Y., Kim, H.G., Chung, C.H. and Ryu, S.O. (2000) Palaeodepositional environment of the Cretaceous Hampyeong Basin, Southwestern Korea. Jour. Korean Earth Sci. Soc., v.21, p.683-694
  32. Zijderveld, J. (1967) A.C. demagnetization of rocks: Analysis of results In Collinson, D.W., Creer, K.M. and Runcorn, S.K.(eds.) Method in Paleomagnetism. Elsevier, London, 254-286p