The Middle Pleistocene Tsumagoi Group, western part of Gunma Prefecture in central Japan is composed mainly of lavas, pyroclastic deposits and lacustrine, fluvial deposits and intercalated with numerous air fall tephra beds. In this study, the three pumice fall beds (KRP, SKP, KKP) which include hornblende mineral so much could be found from the Tsumagoi Group on the southeastern foot of the Azumaya Volcano. The KRP, SKP, KKP were examined in order to correlate with the StPm and KbPm- I, II, III from the Older Ontake Volcano in central Japan, based on their petrographic properties, heavy mineral assemblages and chemical compositions of hornblende measured by microprobe analyses (EDS). Conclusively, the KRP and SKP were correlated with the StPm or KbPm- I, KbPm- II or III in ascending order. The correlation of tephra beds has revealed that the StPm and KbPm- I, II, III are widely distributed in the northeastern side of the Older Ontake Volcano. The ages of these 4 tephra beds were inferred from the stratigraphic relationships with the many dated lavas on the foot of the Older Ontake Volcano. Therefore these tephra beds became valuable marker tephra beds for geochronological studies of the middle Pleistocene in central Japan.

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The sedimentary environment of latest Pleistocene to Holocene of the Kiso river delta is analyzed by means of the electric conductivity method. The results are as follows; 1) Clay beds of the Nohbi Formation deposited under marine water in the present river mouth area and under fresh water in inland areas. The Nohbi transgression prevailed only the present river mouth area. 2) Sedimentary environment of the middle mud member of the Nanyo Formation show marine-brackish water facies in the coastal area and brackish to fresh water facies toward inland areas. The attenuation of marine water with river water is suggested in the back of embayment during the Jomon transgression. 3) The highest stand of the Jomon transgression coincides with the horizon slightly above the K-Ah (Kikai-Akahoya) tephra bed.

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A fossil balaenopterid whale, from the Upper Miocene Shiotsubo Formation in Takasato, Kitakata City, Fukushima Prefecture, northeast Japan, consists of a partial skull, a right tympanic bulla, ribs and vertebral epiphyses. Based mainly on the skull morphology, the specimen is identified as Balaenopteridae genus et species indeterminate. However, the specimen is distinguished by the anteroposteriorly short tympanic bulla from the living balaenopterid whale. This specimen comprises new material for morphological research on the balaenopterid whale in the Late Miocene.

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