蒜山原層中に発達する段裂の解析

Normal faults predominant in the Himzenbara Formation of Pleistocene diatomite indicate extensional stress condition．Many sand veins filling between planes of these faults and some diapirs of massive sandy-diatomite are observed at the central part of a large dome．Stress orientations described by the analyses of conjugate faults are good agreement with structural geometry of this dome．Accordingly，the diapiric doming induced the faulting．This doming may be due to fluidization of sandy diatomite，because flow marks are observed along the diapir margin．Walls of the diapir are also delaminated probably by fluidized sandy diatomite．Moreover，median diameters of the sandy diatomite indicate very fluidizable property．