Southward shift of the Intertropical Convergence Zone in the western Pacific during the late Tertiary: Evidence from ferromanganese crusts on seamounts west of the Marshall Islands
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- Jonguk Kim
- Deep‐sea Resources Research Center Korea Ocean Research and Development Institute Seoul South Korea
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- Kiseong Hyeong
- Deep‐sea Resources Research Center Korea Ocean Research and Development Institute Seoul South Korea
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- Hoi‐Soo Jung
- Marine Environment Research Department Korea Ocean Research and Development Institute Seoul South Korea
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- Jai‐Woon Moon
- Deep‐sea Resources Research Center Korea Ocean Research and Development Institute Seoul South Korea
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- Ki‐Hyune Kim
- Deep‐sea Resources Research Center Korea Ocean Research and Development Institute Seoul South Korea
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- Insung Lee
- School of Earth and Environmental Sciences Seoul National University Seoul South Korea
書誌事項
- 公開日
- 2006-12
- 権利情報
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- http://onlinelibrary.wiley.com/termsAndConditions#vor
- DOI
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- 10.1029/2006pa001291
- 公開者
- American Geophysical Union (AGU)
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説明
<jats:p>Hydrogenetic ferromanganese crusts were dredged from four seamounts in the western Pacific, OSM7, OSM2, Lomilik, and Lemkein, aligned in a NW‐SE direction parallel to Pacific Plate movement. The crusts consist of four well‐defined layers with distinct textural and geochemical properties. The topmost layer 1 is relatively enriched in Mn, Co, Ni, and Mo compared to the underlying layer 2, which is relatively enriched in Al, Ti, K, and Rb and Cu, Zn, and excess Ba. Textural and geochemical properties of layer 2 suggest growth conditions under high biogenic and detrital flux. Such conditions are met in the equatorial Pacific (i.e., between the Intertropical Convergence Zone (ITCZ) and equatorial high‐productivity zone). Layer 2 likely formed when each seamount was beneath the equatorial Pacific along its back track path. On the other hand, layer 1 probably started to grow after seamounts moved northwest from the ITCZ. This interpretation is consistent with the thickness of layer 1 across the four crusts, which increases to the northwest. Ages of the layer 1–layer 2 boundary in each crust, a potential proxy for northern margin of the ITCZ, also increase to the northwest at 17, 11, 8, and 5 Ma for OSM7, OSM2, Lomilik, and Lemkein, respectively. Assuming Pacific Plate motion of 0.3°/Myr, the seamounts were located at 12°N, 11°N, 9°N, and 8°N at the time of boundary formation. This result suggests that the north edge of the ITCZ has shifted south since the middle Miocene in the western Pacific, which agrees with information from the eastern Pacific.</jats:p>
収録刊行物
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- Paleoceanography
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Paleoceanography 21 (4), PA4218-, 2006-12
American Geophysical Union (AGU)