大阪層群 (泉北地すべり地域) の粘土鉱物と生成環境

概要

論文の詳細を見る
The Osaka Group of Pleistocene Age is composed of sandy, gravelly and argillaceous sediments, which are of marine or fresh water origin. Clay mineral compositions of the sediments were determined by the x-ray diffraction method and differential thermal analysis. Cation exchange capacity and the amount of exchanged cation of the sediments were also determined by the Schollenbergers' method. The determination of pH-values of clay suspension was made with a glass electrode. Montmorillonite and halloysite occur in every bed of the sediments, though illite is not found in some beds of fresh water sediments. In general, quantities of montmorillonite and halloysite decrease in marine sediments, compared with fresh water sediments in the upper beds of the Group. Parts of exchange cations are leached from montmorillonites in marine sediments, and therefore pH-values of their clay suspensions become low. It appears that the environment of sedimentation was changed from bay to open-sea environment, as the sedimentation of marine beds proceeded. It seems likely that the clay minerals, especially in marine sediments, were altered by surface weathering with sulfuric acid, which had been produced by oxidation of the sulfide minerals in the sediments.
1971-03-05