The stratigraphic succession of the rocks developed in the eastern margin of the Nara basin is as follows; Rokuyaon gravel bed unconformity Kokuzoyama gravel bed unconformity Shirakawaike formation unconformity Tawara formation unconformity Toyoda formation Fujiwara group Iwabuchi formation unconformity Basement rocks The basement rocks consists mainly of injection gneiss in the northern part and of gneissose granite in the southern part and locally of diorite., Fujiwara group; The Iwabuchi formation, the lower part of the Fujiwara group, is composed chiefly of conglomerate, and is subdivided into three parts by the sedimentary facies., The Toyoda formation, the upper part, consists mainly of tuffaceous fine grained sandstone or mudstone., This group is middle Miocene in age according to the molluscan fossils., Shirakawaike formation; The lower part of this formation is chiefly conglomeratic, but upperwards it becomes muddy or sandy., Among the abundant plant remains derived from the lower part, Metasequoia disticha, Cunninghamia Konishii, Menyanthes trifoliata and others, point to an uppermost Pliocene (I₁) in age., The main geological structure in this area is controlled by two faults with N-S trend (the Takai and the Sanbyaku faults) and by a flexure (the Tenri flexure).,