This area situates at the boundary between Niigata and Gumma prefectures. In the central part of this area, quartz diorite mass is widely distributed and in the eastern and northeastern parts, pre-tertiary rocks are distributed at the tops of the mountains. Pre-tertiary rocks are composed of the so-called "unknown Mesozoic" formation, serpentine and Cretaceous biotite granite. The former two are thermally metamorphosed by the latter. The rocks are also intruded by many diabase dykes. Serpentine includes xenolithic bodies of crystalline schist at the summit of the Tanikawa-dake, Southern and northern parts of this area are widely covered by the Neogene formation. The stratigraphic succession of the Neogene formations in ascending order is as follows: the Shigekura-dake conglomerate formation, Oshoji-no-ataina basalt formation, Mantaro-yama shale formation, Sennokura-yama pyroclastics formation and Akaya shale formation. These formations are considered to belong to Miocene in age and are roughly correlated to the Neogene formation of the Minakami district described by ARAI and KIZAKI (1958). The Akaya formation, the uppermost formation of the area, and lower formations are intruded by quartz diorite mass and are thermally metamorphosed.

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Using the boring cores of the volcanic rocks of the Misasa group, Okayama Prefecture, the measurements of the elastic wave velocities (Vp) in these rocks are discussed with respect to the effect of effective porosity (P) or bulk density (d). These data are shown in Tables 1 and 2, and the relation between V_p and P or d is shown in Fig. 2〜5. When P is less than 7〜8%, we have approximately Vp=a-bP and Vp=-α+βd, where a, b, and β are constants which depend mainly on apparent density (D). When D is larger, in general, these constants are larger, that is, constants of basalt are larger than those of andesite.

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北海道エリモ岬近傍の低位段丘礫層から産出したマンモス象臼歯は,支笏降下軽石層よりも古く,ウルム第1亜氷期後半, WV3に対比されると信ず可き根拠がある,之に対してシベリヤのマンモス象,特に北極圏に知られたものには,層位的に3層準が区別される.即ちエルギ氷期とボッカプチャ氷期の間の温暖期, Riss/Wurm間氷期のものが1つ,その他はラヂオカーボンの値によって,ウルム第1氷期と主ウルム第1氷期の間の温暖期,即ちW1/Wh1の間氷期,第3はAllerod暖期のもので,何れも間氷期のものである.マンモス象は気侯変化につれて移住をくりかえしたが,暖期には北方へ,寒期には南方へとうつったことがわかる.将来の研究によってマンモス象の移動の経過はさらにくわしく知られるであろう.

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