한국해양학회지:바다 (The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY)

  • 제12권4호
  • /
  • Pages.328-336
  • /
  • 2007
  • /
  • 1226-2978(pISSN)
  • /
  • 2671-8820(eISSN)
한국해양학회 (The Korean Society of Oceanography)
권호 표지
DOI QR코드

DOI QR Code

동해 한국대지 코어퇴적물의 특성과 $^{87}Sr/^{86}Sr$ 초기비를 이용한 퇴적시기 규명

Sedimentary Characters of the Core Sediments and Their Stratigraphy Using $^{87}Sr/^{86}Sr$ Ratio in the Korea Plateau, East Sea

  • 김진경 (강원대학교 지질학과) ;
  • 우경식 (강원대학교 지질학과) ;
  • 윤석훈 (제주대학교 해양과학부) ;
  • 석봉출 (한국해양연구원 해양환경특성연구사업단)
  • 발행 : 2007.11.30
PDF 다운로드
⟨ 이전 논문 다음 논문 ⟩

초록

동해 한국대지의 정상부 해저산 사면에서 획득한 코어퇴적물의 퇴적상 분석, 입도와 구성성분 분석, $^{87}Sr/^{86}Sr$ 초기비를 이용한 연대측정을 통하여, 세 단계에 걸친 코어퇴적물의 퇴적과정을 해석하였다. 코어의 하부 구간인 Unit I-a (코어깊이 $465{\sim}587cm$)는 주로 폭풍파에 의해 재동된 천해성 탄산염퇴적물로 이루어져 있으며, 이매패류와 부유성 유공충의 $^{87}Sr/^{86}Sr$ 초기비를 분석한 결과, 퇴적물의 생성시기가 약 $13{\sim}15Ma$(마이오세 중기)로 나타났다. 이는 당시 이 지역 일대가 폭풍파의 영향을 받는 천해환경이었음을 의미한다. Unit I-b (코어깊이 431$\sim$465 cm)는 저탁류에 의해 운반된 퇴적물로 이루어져 있으며, 이매패류와 부유성 유공충의 생성연대는 각각 약 $11{\sim}14Ma$, 약 $6{\sim}13Ma$인 것으로 분석되었다. 이로부터 11 Ma까지는 이 지역 일대가 천해환경을 유지하고 있었으나 그 이후로는 침강하기 시작하였음을 알 수 있다. 그러나 부유성 유공충은 11 Ma 이후에도 지속적으로 생성되어 퇴적물 내에 공급되었으며, 이렇게 생성된 퇴적물들은 연안이나 사면과 같은 근해역에 퇴적되어 있다가 6 Ma 경에 저탁류에 의해 사면 아래로 재동되어 퇴적된 것으로 해석된다. Unit II (코어깊이 $0{\sim}431cm$)는 주로 원양성 퇴적물로 이루어져 있으며, 부유성 유공충의 생성연대가 약 1 Ma로 분석되어, 이로부터 Unit I-b와 Unit II 사이에 약 5 Ma 정도의 결층(hiatus)이 있는 것을 알 수 있다. 또한 Unit II가 퇴적되었던 1 Ma 경에는 이 지역 일대가 충분히 침강하여 현재와 같이 수심 600 m 이상의 심해저환경을 이루고 있었으나, 때때로 주변의 급경사의 사면으로부터 암설류나 저탁류에 의해 조립질 천해퇴적물이나 화산쇄설물 등이 재동되어 퇴적된 것으로 해석된다.

A piston core (587 cm long) was recovered from the upper slope of a seamount in the Korea Plateau. Three episodes of sedimentation were identified based on sedimentary facies, grain size distribution, carbonate constituents and initial $^{87}Sr/^{86}Sr$ ratio of carbonates. The lower part of the core, Unit I-a (core depth $465{\sim}587cm$) is composed of shallow marine carbonate sediments the deposited by storm surges, and is about $13{\sim}15Ma$ (Middle Miocene) based on $^{87}Sr/^{86}Sr$ initial ratio. This suggests that the depositional environment was relatively shallow enough to be influenced by storm activities. Unit I-b (core depth $431{\sim}465cm$) is mostly composed of turbidites, and Sr isotope ages of bivalves and planktonic formaminifera are about $11{\sim}14\;and\;6{\sim}13Ma$, respectively. This indicates that the Korea Plateau maintained shallow water condition until 11 Ma, and began to subside since then. However, planktonic foraminifera were deposited after 11 Ma and redeposited as turbidites as a mixture of planktonic foraminifera and older shallow marine carbonates about 6 Ma ago. Unit II (core depth $0{\sim}431cm$) is composed of pelagic sediments, and the Sr isotope age is younger than 1 Ma, thus the time gap is about 5 Ma at the unconformity. About 1 Ma ago, the Korea Plateau subsided down to a water depth of about 600 m. The sampling locality was intermittently influenced by debris flows and/or turbidity currents along the slope, resulting the deposition of re-transported coarse shallow marine and volcaniclastic sediments.

키워드

참고문헌

  1. Aigner, T., 1985. Storm Depositional Systems. Lecture Notes in Earth Sciences, Springer-Verlag, 3: 174 pp
  2. Bahk, J.J., Chough, S.K., Jeong, K.S. and Han, S.J., 2001. Sedimentary records of paleoenvironmental changes during the last deglaciation in the Ulleung Interplain Gap, East Sea (Sea of Japan). Global and Planetary Change, 28: 241-253 https://doi.org/10.1016/S0921-8181(00)00076-X
  3. Burke, W.H., Denison, R.E., Hetherington, E.A., Koepnick, R.B., Nelson, N.F. and Otto, J.B., 1982. Variation of seawater $^{87}Sr/^{86}Sr$ throughout Phanerozoic time. Geology, 10: 516-519 https://doi.org/10.1130/0091-7613(1982)10<516:VOSSTP>2.0.CO;2
  4. Crusius, J., Pedersen, T.F. and Calvert, S.E., 1999. A 36kyr geochemical record from the Sea of Japan of organic matter flux variations and changes in intermediate water oxygen concentrations. Paleoceanography, 14: 248-259 https://doi.org/10.1029/1998PA900023
  5. Denison, R.E., Koepnick, R.B., Burke, W.H. and Hetherington, E.A., 1998. Construction of the Cambrian and Ordovician seawater $^{87}Sr/^{86}Sr$ curve. Chemical Geology, 152: 325-340 https://doi.org/10.1016/S0009-2541(98)00119-3
  6. Denison, R.E., Koepnick, R.B., Burke, W.H., Hetherington, E.A. and Fletcher, A., 1997. Construction of the Silurian and Devonian seawater $^{87}Sr/^{86}Sr$ curve. Chemical Geology, 140: 109-121 https://doi.org/10.1016/S0009-2541(97)00014-4
  7. DePaolo, D.J. and Ingram, B.L. 1985. High-resolution stratigraphy with strontium isotopes. Science, 227: 938-941 https://doi.org/10.1126/science.227.4689.938
  8. Gorbarenko, S.A., 1993. Reasons for freshening of surface water mass in Sea of Japan during Last Glaciation determined from ratios of oxygen isotopes in plankton foraminifera. Oceanology, 33: 359-364
  9. Gorbarenko, S.A. and Southon, J.R., 2000. Detailed Japan Sea paleoceanography during the last 25kyr: constraints from AMS dating and $\delta^{18}O$ of planktonic foraminifera. Palaeogeography, Palaeoclimatology, Palaeoecology, 156: 177-193 https://doi.org/10.1016/S0031-0182(99)00137-6
  10. Hess, J., Bender, M.L. and Schilling, J.-G., 1986. Evolution of the ratio of strontium-87 to strontium-86 in seawater from Cretaceous to present. Science, 231: 979-984 https://doi.org/10.1126/science.231.4741.979
  11. Hodell, D.A., Mueller, P.A., McKenzie, J.A. and Mead, G.A., 1989. Strontium isotope stratigraphy and geochemistry of the late Neogene ocean. Earth and Planetary Science Letters, 92: 165-178 https://doi.org/10.1016/0012-821X(89)90044-7
  12. Howarth, R.J. and McArthur, J.M., 1997. Statistics for strontium isotope stratigraphy: A robust LOWESS fit to the marine Sr-isotope curve for 0 to 206 Ma, with look-up table for derivation of numeric age. The Journal of Geology, 105: 441-456 https://doi.org/10.1086/515938
  13. Keigwin, L.D. and Gorbarenko, S.A., 1992. Sea level, surface salinity of the Japan Sea, and the Younger dryas event in the Northwestern Pacific Ocean. Quaternary Research, 37: 346-360 https://doi.org/10.1016/0033-5894(92)90072-Q
  14. Kim, J.-M., Kennett, J.P., Park, B.-K., Kim, D.C., Kim, G.Y. and Roark, E.B., 2000. Paleoceanographic change during the last deglaciation, East Sea of Korea. Paleoceanography, 15: 254-266 https://doi.org/10.1029/1999PA000393
  15. Koepnick, R.B., Denison, R.E., Burke, W.H., Hetherington, E.A. and Dahl, D.A., 1990. Construction of the Triassic and Jurassic portion of the Phanerozoin curve of seawater $^{87}Sr/^{86}Sr$. Chemical Geology, 80: 327-349
  16. Koepnick, R.B., Burke, W.H., Denison, R.E., Hetherington, E.A., Nelson, H.F., Otto, J.B. and Waite, L.E., 1985. Construction of the seawater $^{87}Sr/^{86}Sr$ curve for the Cenozoic and Cretaceous: supporting data. Chemical Geology, 58: 55-81 https://doi.org/10.1016/0009-2541(85)90179-2
  17. Lee, E. and Nam, S., 2003. Freshwater supply by Korean rivers to the East Sea during the last glacial maximum: a review and new evidence from the Korea Strait region. Geo-Marine Letters, 23: 1-6 https://doi.org/10.1007/s00367-003-0118-1
  18. Lee, E. and Nam, S., 2004. Low sea surface salinity in the East Sea during the last glacial maximum: review on freshwater supply. Geosciences Journal, 8: 43-49 https://doi.org/10.1007/BF02910277
  19. Lee, K.E. and Kim, K.-R., 2002. Past sea surface temperature of the East Sea inferred from alkenone. Journal of the Korean Society of Oceanography, 37: 27-34
  20. Lee, S.H. and Chough, S.K., 2001, High-resolution (2-7 kHz) acoustic and geometric characters of submarine creep deposits in the South Korea Plateau, East Sea. Sedimentology, 48: 629-644 https://doi.org/10.1046/j.1365-3091.2001.00383.x
  21. Lee, S.H., Chough, S.K., Back, G.G. and Kim, Y.B., 2002. Chip (2-7 kHz) echo characters of the South Korea Plateau, East Sea: styles of mass movement and sediment gravity flow. Marine Geology, 184: 227-247 https://doi.org/10.1016/S0025-3227(01)00283-3
  22. Oba, T., Kato, M., Kitazato, H., Koizumi, I., Omura, A., Sakai, T. and Takayama, T., 1991. Paleoenvironmental changes in the Japan Sea during the last 85,000 years. Paleoceanography, 6: 499-518 https://doi.org/10.1029/91PA00560
  23. Park, B.-K., Shin, I.C. and Han S.-J., 1997. East Sea (Japan Sea) Climate Event during the Younger Dryas and Last Deglaciation. Ocean Research, 19: 257-264
  24. Tada, T., 1994. Paleoceanographic evolution of the Japan Sea. Palaeogeography, Palaeoclimatology, Palaeoecology, 108: 487-508 https://doi.org/10.1016/0031-0182(94)90248-8
  25. Tada, R., Irino, T. and Koizumi, I., 1999. Land-ocean linkages over orbital and millennial timescales recorded in late Quaternary sediments of the Japan Sea. Paleoceanography, 14: 236-247 https://doi.org/10.1029/1998PA900016
  26. Tamaki, K., 1988. Geological structure of the Japan Sea and its tectonic implications. Bulletin of Geological Survey of Japan, 39: 269-365
  27. Tamaki, Y. and Kimura, N., 1991. Backarc extension versus continental breakup: petrological aspects for active rifting. Tectonophysics, 197: 127-137 https://doi.org/10.1016/0040-1951(91)90037-S
  28. Yoon, S.H. and Chough, S.K., 1995. Regional strike slip in the eastern continental margin of Korea and its tectonic implications for the evolution of Ulleung Basin, East Sea (Sea of Japan). Geological Society of America Bulletin, 107: 83-97 https://doi.org/10.1130/0016-7606(1995)107<0083:RSSITE>2.3.CO;2