^<230>Thを用いたチリ沖中緯度域における第四紀後期生物起源粒子フラックス変動  [in Japanese] ^<230>Th-normalized Fluxes of Biogenic Components from the Central Chilean Margin during the Late Quaternary  [in Japanese]

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    • 原田 尚美 HARADA Naomi
    • (独) 海洋研究開発機構地球環境変動領域 Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology
    • 川上 創 KAWAKAMI Hajime
    • (独) 海洋研究開発機構むつ研究所 Mutsu Institute for Oceanography, Japan Agency for Marine-Earth Science and Technology
    • 福田 美保 [他] FUKUDA Miho
    • (独) 海洋研究開発機構地球環境変動領域 Research Institute for Global Change, Japan Agency for Marine-Earth Science and Technology
    • 松本 剛 MATSUMOTO Takeshi
    • 琉球大学理学部物質地球科学科 Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyu


 Throughout geologic time, variations of atmospheric CO<sub>2</sub> partial pressures (<i>p</i>CO<sub>2</sub>) have been associated with climate change. During glacial periods, increased productivity and an efficient biological pump in the North Pacific, equatorial Pacific, and Southern Oceans may have contributed to low atmospheric <i>p</i>CO<sub>2</sub>. Furthermore, changes in global ocean ventilation would have been considered to be among the most effective controllers of variations of atmospheric <i>p</i>CO<sub>2</sub> glacial-interglacial time scale. However, there is still some controversy as to whether ventilation was effective everywhere during glacial periods, and whether intensification of marine productivity resulted in a decrease of atmospheric <i>p</i>CO<sub>2</sub>. Resolving this controversy requires more data from many regions regarding temporal changes in past export fluxes of biogenic materials, especially in the upwelling area, where active ocean ventilation and biological production are observed. The aim of this study is to identify changes in the <sup>230</sup>Th-normalized export flux of biogenic components commonly used as proxies for paleoproductivity—namely total organic carbon (TOC), calcium carbonate (CaCO<sub>3</sub>), biogenic opal (Si<sub>OPAL</sub>), and opal and CaCO<sub>3</sub> ratio (Si<sub>OPAL</sub>/CaCO<sub>3</sub>)—as recorded in a sediment core from 36°S off the central–south Chilean coast. The <sup>230</sup>Th-normalized fluxes of biogenic components were low from 22,000 to 15,000 calendar years before the present (cal yr BP), indicating reduced primary productivity. From 13,000 to 10,000 cal yr BP, the <sup>230</sup>Th-normalized flux of biogenic components increased, thereafter dropping between 8000 and 5000 cal yr BP, and again increasing slightly in the late Holocene (< 5000 cal yr BP). The changing <sup>230</sup>Th-normalized fluxes of biogenic components are linked to upwelling activity, which was at its maximum during the late deglaciation during the past 22,000 yr. The high fluxes off the central–south Chilean coast might in part be not only due to enhanced coastal upwelling but also related to enhanced upwelling at higher latitudes of the polar frontal zone in the entire Southern Ocean, which would be related to the north-south migration of Southern Westerly Winds.


  • Journal of Geography (Chigaku Zasshi)

    Journal of Geography (Chigaku Zasshi) 121(3), 555-569, 2012-06-25

    Tokyo Geographical Society

References:  65

Cited by:  3


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