The Middle Pleistocene Terabayashi Formation around Mt. Ibuki, in Terabayashi, Maibara City, Shiga Prefecture, central Japan, interbeds the Terabayashi I and II volcanic ash layers that were laid down about 248-247ka ago (Late Middle Pleistocene) and which lie above the Aso-1 volcanic ash layer. The sediments correspond to oxygen isotope stages 8 to 7, a cold period leading to a warm period.
We reconstructed the paleovegetation and paleoclimate based on plant macrofossils, fossil pollen, and insect fossils from these sediments. 1) The vegetation of Mt. Ibuki and its surroundings was a mixed evergreen coniferous and deciduous broadleaf forest containing Pinaceae, Betulaceae, and Rosaceae, including such dominant trees as Pinus koraiensis, Tsuga diversifolia, Abies homolepis, Betula ermanii, B. platyphylla, B. grossa, Malus toringo, and Rubus. At present these species inhabit the upper cool temperate to subarctic zone. 2) The paleoenvironment was reconstructed in the Terabayashi area as follows : a small swamp in which Potamogeton octandrus and Chara grew and where insects such as Lithochlaenius noguchii and Bembidion subsisted and lived ; wetlands covered with Alnus japonica, Rubus, Cyperus, Carex, Polygonum, and Potentilla, and where insects such as Chrysosplenium and Plateumaris lived ; and sun-loving plants such as Kummerovia striata, Artemisia, and Solanum grew and the forest which was composed of Betula grossa, B. platyphylla, and Abies homolepis existed. In the adjoining mountains, Tsuga diversifolia grew on the ridges ; Abies homolepis, Corylus heterophylla, Malus toringo, and Phellodendron amurense grew on the more gradual slopes ; and Pterocarya rhoifolia and Juglans mandshurica var. sachalinensis grew on the valley sides. Herbs such as Melandryum, Coptis, Thalictrum, Impatiens textori, Angelica acutiloba, and Cornus cf. chamaepericymenum grew on the forest floor, where Carabus beetles also lived. In the upper parts of the mountains a mixed evergreen coniferous and deciduous broadleaf forest dominated by such trees as Pinus koraiensis, Tsuga diversifolia, and Betula ermanii existed. 3) The plant fossil assemblages from the lowermost part to the lower middle part of the Terabayashi Formation demonstrate a dry and cool temperate to subarctic paleoclimate. Fossil pollen shows a change from this dry and cold climate to wet and temperate conditions, with a decrease in Abies, Tsuga, Picea, and Betula but an increase in Fagus and Quercus subgen. Lepidobalanus, when the upper middle strata in the sequence were deposited.

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We evaluate the late Quaternary activity of the Uozu fault zone in the eastern part of Toyama Prefecture. The Uozu fault zone dislocates fluvial terrace surfaces severely, but the slip rate is not well known because the terrace surfaces are not well dated. We estimate the formation ages of fluvial terrace surfaces from aerial photo interpretation, field survey, and chemical analysis of tephra particles in loess deposits. Loess deposits on fluvial terrace surfaces include cryptotephras such as U-1 (120-140ka), K-Tz (Kikai-Tozurahara : 90-95ka), Aso-4 (85-90ka), DKP (Daisen-Kurayoshi : 55-60ka), and AT (Aira-Tn : 25-30ka). LH1 terrace surface is slightly older than the 55-60ka DKP tephra. M1 terrace surface is older than the 90-95ka K-Tz tephra. H2, H3, and M1 terrace surfaces are estimated to be 280-310ka, 240-260ka, and 155-165ka, respectively, as long as the accumulation rate of loess deposits above each surface is constant. Vertical slip rates of faults are calculated using these terrace formation ages : over 0.24-0.46m/ky at the central part of the fault zone, and 0.13-0.24m/ky at the southern part of the zone. Maximum vertical slip rate of the Uozu fault zone has been considered to be over 1m/ky. But the rate might be overestimated because terrace ages are being revised to be older than previously reported. Future study is required to clarify the underground geological structure which records vertical displacement on faults for evaluation of the activity of the Uozu fault zone.

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The timing of the glacial advances and volcanic activities on Mt. Tateyama (3,015m) and Tateyama Volcano in the Hida Range in central Japan during the late stade of the last glacial period were clarified based on three moraines and their stratigraphic relationships with volcanic ejecta. The late stade was subdivided into Tateyama Stades I (just before 29cal ka), II (18-20 ¹⁰Be ka) and III (10-11 ¹⁰Be ka). The glaciers during the late stade attained their maximum advances in Tateyama Stade I and retreated with time. The maximum glacial advances during the late stade were caused just before 29cal ka in MIS 3 on the high mountains in the Hida Range simultaneously. Between Tateyama Stades I and II, the Tateyama Volcano gave rise to phreatic explosions that fragmented a lava layer overlying explosion crater. The fall of the lava fragments, however, did not trigger off the start of the glacial retreat and advance on Mt. Tateyama.

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The Plio-Pleistocene Gotsu Group is widely distributed in central and western Shimane Prefecture, southwest Japan. The chemical compositions of volcanic glass shards and constituent minerals in tephras collected from seven sites in the Gotsu Group were examined for correlation of the Plio-Pleistocene successions. Rhyolitic glass shards (SiO₂=77.0-79.8wt.%) were found in four tephra beds. Common hornblende and zircon occur in all tephras. These tephras were divided into four groups based on their association of mafic minerals : (1) olivine, (2) orthopyroxene and biotite, (3) cummingtonite and biotite, and (4) cummingtonite.
Combining the assemblages and chemical compositions of constituent minerals with fission track ages, two tephra beds belonging to group (2) dated at 1.7±0.2Ma, and two tephra beds from group (3) with ages of 1.1±0.1Ma can be correlated. Tephra beds in group (3) may be derived from the Plio-Pleistocene Oe-Takayama volcano.
The tephras described with clear characteristics and reliable radiometric ages will be valuable for correlation of the Plio-Pleistocene successions in southwest Japan outside Shimane as well as in the Gotsu Group.

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