The marine terrace of Hiradoko, 20-55 m high above present sea level, seems to be a good record of history during the late Pleistocene in Japan Sea region of Japan. A study of terrace deposits including several shell beds reveals that there occurred two distinct phases of transgression (rise of sea level) during the late Pleistocene, probably due to glacial eustatic movement. They are called Hiradoko and Uji phases, respectively perhaps corresponding to Shimosueyoshi and Musashino phases in the Kanto region of Japan. Hiradoko phase may be correlated to the Riss-Wurm interglacial, and attained its maximum rise upto +60 m above present sea level. Uji phase is a minor one preceding the maximum regression of the Wurm glacial, showing 20 m± rise of sea level. The present article contains description of geomorphology and geology of basement, field evidence, list of fossils, and the data of the Alluvial deposits. A summary of the Pleistocene deposits is shown on Fig.18. The history during late Pleistocene is diagrmmatically shown in Fig. 21. Several paleogeographic maps and a series of schematic profiles through Hiradoko age will be serviceable to understand the historical change.

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The Nohi rhyolites with subordinate sediments (Adera formation and Schirakawaguchi formation) are widely developed in the non-metamorphosed Paleozoic terrain, and form a large elongated mass which intersects with a trend of the Paleozoic formations at nearly right angle. They occupy an area of about 5,000 km^2 and seem to have a volume of about 3,000 km^3. The Nohi rhyolites were called, hitherto, "quartz porphyries", but now they are revealed to be the horizontal piles of rhyolite welded tuff as a whole, so we rename them "Nohi rhyolites". The rocks are compact, mostly massive and dark gray in color, and they have highly porphyritic appearance due to phenocrystic quartz, plagioclase (oligoclase-andesine), potash feldspar and mafic minerals in order of abundance. These phenocrysts show, characteristically, angular or corroded forms. Mafic minerals are brown biotite, green hornblende, brown hornblende, augite, hypersthene, etc., being altered to secondary minerals in almost all cases. The amount of each mafic mineral is quite variable. Matrix of the rocks is composed chiefly of volcanic glass and pumice fragments which are tightly welded and remarkably devitrified to fine-grained silica minerals. Lenticular aggregates of rather well-formed quartz and potash feldspar are sometimes included in the matrix. In addition to the above-mentioned minerals, the rocks bear, abundantly in some parts, angular lithic fragments such as Paleozoic rocks and rhyolites, the latter being assumed as congnate inclusion. Besides such porphyritic rhyolite welded tuff, several layers of non-porphyritic glassy welded tuff and andesite welded tuff occur as minor members. At the eastern border of the mass, the Nohi rhyolites accompanied with the Adera formation overlie the Paleozoic rocks unconformably. The formation mainly composed of conglomerate, mudstone and tuff is covered by or intercalated in the rhyolites. This fact proves the presence of hiatus during the deposition of the welded tuff. On the other hand, along the western border of the mass, the rhyolites are often in contact with the Paleozoic rocks by the intrusive-like relation. There, the Paleozoic rocks are strongly disturbed and crushed by faults of NW-SE trend. At the neighbouring area of Schirakawaguchi, peculiar deposits (the Schirakawaguchi formation) chiefly composed of unsorted breccias of the Palezoics rocks which seem to be fault-breccias lie between the rhyolites and Paleozoic rocks. Moreover, such deposits are also found in upper horizon of the rhyolites at some places along the western border. Judging from the modes of occurrences of the formation, it is assumed that faulting and succeeding eruption of the rhyolites occurred repeatedly. The rhyolites are succeeded, soon after their consolidation, by the intrusion of granite porphyry which mostly dyke-formed and sometimes stock-formed, and lastly by the batholithic intrusion of biotite granite. Such a series of magmatism (rhyolite-granite prophyry-granite) seems to be one of the most characteristic igneous events in the late Mesozoic age, not only in Japan, but also in the wide area, so-called Circum Pacific zone.

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The superficial deposits on the Kanto plain consist mainly of Pleistocene volcanic ashes, commonly called "Kanto Loam". They are excellent time-markers in the correlation of topographic surfaces and Quaternary deposits in the Kanto district throughout their extent. From the stone implements of Palaeolithic aspect, several marine transgressions and regressions and climatic records, it was possible to establish a new correlation chart as shown in Fig.4. It probably provides a stratigraphic standard for the Quaternary research in Japan. The above mentioned marine transgressions and regressions may probably be indications of the glacio-eustatic swinging of the sea-level.

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At the eastern slope of the Akaishi Massif, Itoigawa-Shizuoka tectonic line which divides Honshu island into N. E. Japan and S. W. Japan, runs between undivided Mesozoic Setogawa group of Shimanto zone of Akaishi massif and Miocene green tuff Misaka group of southern Fossa Magna region. It may be concluded that the tectonic line would occur to associate with the formation of zonal arrangement of Shimanto zone of Akaishi massif and reactivity would continue to recent. Further more, those zonal arrangement are expected enveloping under green tuff region of southern Fossa Magna region, and then, reactivity of those structure would brought some fundamental effects to evolution of covering Neogene deposits. Along that tectonic line, mylonite zone, silicified zone, and phyllitic rock zone are distributed zonally from west to east. Among them, mylonite zone and silicified zone are characterized by vast amount of porphyrite-aplite-quartz vein complex and they accept syntectonic crushing.

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