SUMMARYCoralloid speleothems are commonly distributed in Togawa-Sakaidani-do Cave in .• Miyazaki Prefecture, Central Kyushu, but their speleological study has not heretofore been achieved. Light and scanning microscopes analyses revealed that coralloid speleothems consist of alternating layers of diatom colonies, detrital minerals and clay. Electron microprobe analysis shows coralloid speleothems to be siliciferous.This paper assert that diatom (genus Melosira) is one of the important contributors to siliceous coralloid speleothems in the threshold zone at noncalcareous caves.
Many andesitic intrusions are exposed along the Median Tectonic Line (MTL) in northwest ern Shikoku, Japan. Three dikes along the MTL and one intrusion occurring close to it were dated by the K-Ar method to estimate when the fault movement ceased. The dikes and intrusion are not deformed by the movement. The results give 15.1 to 15.4 Ma excluding severely altered one. The MTL in northwestern Shikoku region has not been active since about 15 Ma. Although a similar attenuation of active movement of the MTL during middle Miocene has been reported, the fault movement has continued in the other areas of southwestern Japan as demonstrated by Active Fault Research Group (1980). This may suggest that block displacement has been dominant since middle Miocene in the studied area. The age of the samples also indicates that the volcanic activity of Seto-uchi region started 15Ma in northwestern Shikoku.
SUMMARYThe wad-minerals from limestone caves of Yugoslavia, China and Japan were studied. X-ray diffraction analysis revealed that five minerals; birnes site, lOA-manganite, pyrolusite, todorokite and goethite. The heavy metal elements, Mn. Zn, Fe and Cr have been detected by X-ray fluore~cence analysis and their contents were roughly determined. The input sources of man · ganese and other metal elements can be proposed to be the condensation water introduced directly from the covering soils formed by the continental weathring, to be the corrosive water introduced r eworking from the limestone .
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