津久見石灰岩（東部地区）の層序と構造

Tsukumi limestone group, distributed in the eastern part of Oita Prefecture, is a conspicuous member of the Chichibu Terrain of the Outer Zone of Southwest Japan.
The stratigraphic succession of the group is in descending order as follows:
Permian formations
Upper formation
Dolomitic, oolitic limestone
Limestone conglomerate
Middle formation
Dark-grey or light-grey limestone, containing the Yabeina globosa faunule and Neoschwagerina-Waagenophyllum fauna.
Limestone-conglomerate, containing the Neoschwagerina-Verbeekina faunule.
Lower formation
Black sandy shale and sandstone
Grey limestone, yielding the Pseudoschwagerina-Pseudofusulina-Stylidophyllum fauna.
Carboniferous formation
Oolitic, grey limestone, containing the Fusulinella faunule.
The group is covered by the so-called Aso welded-tuff, loam and gravel bed.
The geologic structure of the Tsukumi limestone group in the Suisyozan area is characterized by the zonal arrangement of the limestone formations and intercalations, which seems to be a result from the deformation of synclinorium. The structure is modified by many strike-faults or subparallel ones which are accompanied with the conspicuous fault-zone composed of sheared blocks of limestone and sandy-shale.
Many normal or slightly diagonal faults cut the structure mentioned.
The Tsukumi limestone group is separated from the adjoining non-calcareous formations, the Okukawachi and the Kozono, by the manifest faults dipping northwardly or vertically.