| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2006: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 2005: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Research Abstract |
This study airas to characterize Quaternary tephras in southern Kyushu based on the chemical compositions of their volcanic glass shards using EPMA, and to get fundamental data on the correlation and chronology of those tephras. In this study, I focused on the late Pleistocene and Holocene tephras of Satsunan Islands including Tokara islands, in which there have been few systematic tephrochronological studies. EPMA analysis made it clear the chemical properties of large plinian tephras in Kuchierabujima, Kuchinoshima and Akusekijima Islands of Tokara Islands, and of middle Pleistocene marker tephras in Yakushioma Island.In addition, Landform evolution and palaeo-environment history were clarified based on the identification and chronolog on other tephras relevant to tephra characterizations of those tephras. The main results are as follows. Three marker pumice falls recognized in Kuchierabujima, Kuchinoshima, Akusekijima Islands, can be distinguished based on their chemical properties. Those tephras rich in Si02 are all rhyolitic and the products of big plinian eruptions, suggesting that those tephras are distributed over Satsunan Islands, Osumi and Satsuma peninsulas far distant from the volcanic islands. Middle Pleistocene vitric ash-Anbo tephra-and gigantic pyroclastic flow-Koseda pyroclastic flow-in Yakushima Island have distinct chemical properties in their glass shards, suggesting that those tephras can be identified in extensive area across and around the Japanese Island.
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