北九州の段丘地形とAso-4火砕流堆積物

概要

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The results obtained were summarized as follows; (1) The fluvial terrace have developed in Kitakyusyu Regions. These terrace were- divided into three terrace groups, namely, the higher terrace surface, the upper terrace surface, and the lower terrace surface. The destribution of Red soil was restricted on relatively higher terrace surface. Red weathering crust covered with Aso-4 pyroclastic flow deposits distributed on the upper terrace surface. (2) The Aso-4 pyroclastic flow was one of the largest of activities of Aso volcano. (3) Aso-4 pyroclastic flow covered extensive area of Kyusyu round the Aso caldera and western part of Honsyu. (4) The ash, named the Aso-4 ash, was a fine-grained ash, consisting of bubble wall glass shard and brown hornblende, hyperthene and Magnetite. (5) Especially Aso-4 pyroclastic flow changes into the facies of white clay called as Yamenendo at its fill-top, and this is most extensively distributed as tephrochronological key bed in northern and middle Kyusyu. (6) The heavy mineral assemblage of Yamenendo was composed of brown hornblende, hyperthene, and augite. (7) The age of the upper terrace surface is at least older than 1.2-1.3×10^5 years.
日本ペドロジー学会の論文
1998-06-30