新期榛名火山の主要な3回の火砕噴火の噴出物について，炭素14年代値が得られたので報告する．得られた年代値は白川火砕流堆積物から2件，二ッ岳渋川テフラから3件，二ッ岳伊香保テフラから4件である．白川火砕流から得られた年代値は45 ka であり，これは新期榛名火山最初で最大の火砕噴火の年代を示す．二ッ岳渋川テフラから得られた年代値は1540～1640 yr BP であり，また二ッ岳伊香保テフラからはいずれも1480 yr BP の年代値が得られた．これらの結果は，二ッ岳渋川噴火は5世紀末～6世紀初頭にかけて，伊香保噴火は6世紀後半から7世紀初頭にかけて発生したことを示す．
Geological Survey of Japan, AIST has been carrying out the cooperative research entitled "Hydrological and geochemical research for earthquake prediction in Taiwan" with Disaster Prevention Research Center, National Cheng-Kung University, Taiwan since 2002. We made much contribution to clarifying the mechanism of groundwater changes and their recoveries related to the 1999 Chichi earthquake, constructing a groundwater observation network composed of 16 wells in Taiwan and understanding the earthquake-related groundwater changes observed by the new groundwater observation network through this cooperative research. In Taiwan seismicity is more active and crustal deformation is more rapid than in Japan. Therefore observation and analysis of groundwater changes related to earthquake and crustal deformation in Taiwan will enable us to make rapid progress in hydrological and geochemical research for earthquake prediction. This cooperative research will also give important information for evaluation of long-term groundwater changes in tectonically active areas like Japan and Taiwan.
Late Triassic radiolarian fossils were extracted from siliceous mudstone in an accretionary complex of the Ashio Terrane in the Kamo district (Quadrangle series 1:50,000 of the Geological Survey of Japan), Niigata Prefecture, Japan. The siliceous mudstone occurs as a block within a muddy matrix. The siliceous mudstone also belongs to the upper unit of the Senmi Complex, which is distributed widely in the Kanbara Mountains within the Kamo district. The fauna in the siliceous mudstone consists mainly of species of the genera Canoptum, Betraccium, Cantalum and Fontinella, including Canoptum sp. cf. C. rhaeticum, Fontinella sp. cf. F. clara, Fontinella sp. cf. F. primitiva etc. Based on radiolarian biostratigraphy of these taxa previously documented elsewhere, the radiolarian fauna studied was dated to the Late Triassic (Rhaetian). This is a first report of Triassic radiolarian fossils from clastic rocks of the Ashio Terrane in the Kanbara Mountains; thus, this find contributes to reconstructions of oceanic plate stratigraphy of the Ashio Terrane in this region.