The carbon and oxygen isotope ratios of calcite in calcite nodules with or without apatite from the Miocene Tomikusa Group in the south of Nagano Prefecture were measured. The isotope ratios are considerably scattered in the δ¹³C versus δ¹⁸O diagram. However, the isotopic ratio of calcite from each sampling locality shows a linear trend with different positions and slopes on the δ¹³C versus δ¹⁸O diagram. The trends converge to a narrow region of δ¹³C = −5~+1‰ and δ¹⁸O = 15~16‰, when the trends are extended to the low δ¹⁸O direction. The convergence zone was named PC (Position of Convergence), which corresponds to the isotopic ratio of calcite in equilibrium at 45°C with meteoric water of δ¹⁸O = −9‰ in the southern part of Nagano Prefecture. Calcite nodules of the Tomikusa Group were formed by early diagenesis of sulfate reduction to methane fermentation stages, and were subjected to ground water infiltration after the Tomikusa Group uplifted in the late Miocene to the Pliocene. Consequently, carbon and oxygen isotope ratios shifted toward the PC to varying degrees. Clinoptilolite and opal-CT occur in the rocks of the Tomikusa Group. It is inferred that the isotopic alteration of calcite nodules occurred during burial metamorphism with the formation and infiltration of silicic acid-rich aqueous solutions.

A fossil palatine identifiable as the fossil genus Polymerichthys (Aulopiformes, Alepisauroidei, Polymerichthyidae) is reported from the Middle Miocene Iseyama Formation (Serravallian), Ueda City, Nagano Prefecture, central Japan. The palatine arranges six well preserved palatine teeth, and the teeth have a close affinity in morphology with other fossil Polymerichthys specimens. As diagnostic compared the other fossil specimens on the basis of a possible palatine tooth morphology, the tooth is strongly similar to that of Polymerichthys nagurai in the following characteristics: the appearance is slender and saber-like; the tooth tapers toward an apex and inclines anteriorly; and each cutting edge does not possess a barb. The tooth is noteworthy for being anteriorly inclined, a characteristic shared only with Polymerichthys and Anotopterus (Paralepididae), and for not being found anywhere in other teleosts. Polymerichthys sp. from the middle Miocene of Nagano Prefecture represents the second record of polymerchthyid fish from Japan as well as the fifth record from the world. The present fossil evidence concisely suggests that Ueda City and the vicinity in Nagano Prefecture, that is located in the central part of the northern Fossa Magna Region, faced the northwestern Pacific Ocean, at least during the depositional age of the lowest part of the Iseyama Formation.

Whole-rock geochemical compositions and the K-Ar age of welded tuff gravels of the Oda coast, San’in district, southwest Japan were examined. The welded tuff gravels are mostly massive vitrophyre characterized by strong welding and an eutaxitic texture. Phenocrysts are mainly plagioclase sometimes corroded, and quartz grains of which are strongly corroded. The estimated age of the welded tuff gravel sample is 52.3 Ma. The welded tuff gravel samples show SiO₂ contents varying 73-76 wt%. These rocks of welded tuff are not distributed upstream of the Oda River and the surrounding areas. They might have been eroded from their source area and transported by fluvial processes to the river mouth. Now they remain at the coast due to their endurability and high hardness.

The Guadalupian Follicucullus assemblage, which is made mostly of the genus Follicucullus (Radiolaria), was found from Arida City, Wakayama Prefecture. The fossil locality in the southern area of Arida City is geologically attributed to the Northern Chichibu Belt, which is occupied by such lithologies as chert, sandstone, mudstone and green rocks. Radiolarian fossils were extracted with diluted hydrofluoric acid from a bedded chert layer exposed at the Mandarin Coastal Street. The occurrence of Follicucullus porrectus Rudenko and Follicucullus cf. scholasticus Ormiston et Babcock and the lack of Follicucullus charveti Caridroit et De Wever indicate a Capitanian horizon of the Guadalupian Series. This is the first report of the occurrence of Permian radiolarians from the Arida City area. The significance of the occurrence of Permian chert in the Northern Chichibu Belt is discussed as well as the formative factor of the Follicucullus assemblage (deep water current or oceanic environmental change).