Ocean and Polar Research

Korea Institute of Ocean Science & Technology (한국해양과학기술원)
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Paleo-latitude of the Intertropical Convergence Zone in the Northeast Pacific during Late Cenozoic

신생대 후기 북동태평양 지역 적도수렴대의 위치변화

  • 형기성 (한국해양연구원 해저환경.자원연구본부 심해저자원연구센터) ;
  • 김기현 (한국해양연구원 해저환경.자원연구본부 심해저자원연구센터) ;
  • 지상범 (한국해양연구원 해저환경.자원연구본부 심해저자원연구센터) ;
  • 유찬민 (한국해양연구원 해저환경.자원연구본부 심해저자원연구센터)
  • Published : 2004.06.30
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Abstract

The Intertropical Convergence Zone (ITCZ), where the southeast and northeast trade winds converge, is the effective climatological barrier that separates the southern and northern hemispheres in dust budget. Asian and N. American dusts dominate in fhe Pacific north of the ITCZ, while Central and S. American dust prevails south of the ITCZ. In order to understand the nature of latitudinal and depth-related variations of mineral composition in terms of relative position to the ITCZ, deep-sea core sediments were collected from $9^{\circ}N$ to $17^{\circ}N$ at a $2^{\circ}N$ interval along the $131.5^{\circ}W$ meridian and analyzed for mineral composition. The amount of illite in surface sediments decreases gradually from 65% at $17^{\circ}N\;to\;31^{\circ}N$ to 31% at 9f. In contrast, smectite increases from 11% to 56% southward. The observed mineralogical variation toward the ITCZ is attributed to the increased supply of volcaniclastic material transported via the southeast trade winds from the Central and South America source regions. Smectite-illite transition, a phenomenon that the amount of smectite increases over illite, occurs at around $10^{\circ}N$, the northern margin of the ITCZ. This result indicates that the change in latitudinal position of the ITCZ in geologic past could be recorded as a form of smectite-illite transition in deep-sea cores. The studied cores show down-core variation of mineral composition from illite-rich at the surface to smectite-rich clay suit at depths, similar to the latitudinal variation. The smectite-illite transitions observed in these cores are likely the records of changes in latitudinal position of the ITCZ. The depth and age of smectite-illite transition is getting shallower and younger toward equator, implying that the ITCZ was located farther north during late Tertiary and has shifted southward to the present position of $5^{\circ}N-10^{\circ}N$.

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