The Junicho Formation consists of late Pliocene to early Pleistocene marine sediments that crop out near Himi City, northwest of Toyama Prefecture. The Junicho Formation was reported to include the Plio-Pleistocene boundary based on calcareous nannofossil biostratigraphy. Sedimentary cycles derived from glacioeustatic sea-level change were also reported from the middle part of the Junicho Formation. In order to date of the middle part of the Junicho Formation, the authors analyzed chemical components of volcanic glass in volcanic ash beds by energy dispersive X-ray spectrometry (EDS) to correlate with widespread volcanic ashes in central Japan. The authors also measured paleomagnetic directions of the sediments. The results showed that the volcanic ash beds in the Junicho Formation correlate with the Hotaka-Kd39 and Ebisutoge-Fukuda tephras which were previously reported from horizons of Plio-Pleistocene boundary in the Kazusa Group at the Boso Peninsula. Examination of the magnetostratigraphic relationship of the Hotaka-Kd39 and Ebisutoge-Fukuda tephras in the Junicho Formation proved that they were consistent with those in Boso Peninsula. Horizons of the Hotaka-Kd39 and Ebisutoge-Fukuda tephras belong to the sedimentary cycle III in the middle part of the Junicho Formation, and therefore the sedimentary cycles of the middle part of the Junicho Formation clearly include the Plio-Pleistocene boundary. In the Junicho Formation, the Hotaka-Kd39 and Ebisutoge-Fukuda tephra deposited during relative sealevel highstand that estimated Oxygen Isotope Stage 63.

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The lacustrine sediments of the Takatomi Lowland include the widespread volcanic ashes called Aso-4, AT, and K-Ah derived from southern Kyushu. The sediments have been deposited continuously since the early Last Glacial Period, marine isotope stage 5b. Pollens from 16.5m boring cores of these sediments were analyzed to discuss the vegetation and climate history, to correlate MIS chronology, and to clarify the distributions of vegetation by correlating other site data at each age. The fossil pollen assemblages from the Takatomi Lowland sediments are divided into ten pollen zones, TK-I to X. At the age of MIS 5b, the Takatomi Lowland was occupied by warm temperate broadleaf forests of Cyclobalanopsis, and the climate was warm and wet. As the pollen grains of Cryptomeria and Sciadopitys were prevalent at the age of MIS 5a, it is thought that there was abundant precipitation. At the age of MIS 4, as the pollen grains of subboreal coniferous trees increase abruptly, it became colder and dryer. At the age of MIS 3, the climate became warmer than at the previous age as the pollen grains of cool temperate deciduous broadleaf forests prevailed. About 31, 000 years ago (MIS 2, full glacial period), the climate became dryer and colder suddenly, as shown by the pollen grains of subboreal coniferous trees and deciduous broadleaf trees such as Betula and Corylus-Myrica, which grow in the cool temperate zone. About 14, 000 years ago, as the pollen grains of coniferous trees disappeared abruptly, a warmer climate increased the pollen grains of deciduous trees such as Lepidobalanus and Corylus-Myrica. In the late glacial period, the pollen grains of Ilex prevailed, and since 3, 000 years ago the pollen grains of the warm temperate evergreen broadleaf forests of Cyclobalanopsis have prevailed. Comparing the pollen assemblage data from the Hokuriku District located along the Japan Sea, the Takatomi Lowland on the Pacific Ocean side was thought to be only at the age of MIS 5a, when the climate was humid as inferred from the presence of pollen such as Cryptomeria and Sciadopitys; but at other ages the Pacific Ocean side was dryer than Japan Sea side.

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Onikobe Ikezuki tephra (O-Ik: ca 250 ka), which consists of vast pyroclastic flow deposits and their underlying fall unit, is a middle Pleistocene marker tephra in Miyagi Prefecture, eastern foot of the Ou Backbone Range, in the central part of Northeast Japan. This study reports that O-Ik tephra was also found in Mukaimachi and Shinjo Basins located just at the western foot of the Range. Identification of the tephras is based on an index of glass and opx and major chemical compositions of glass shards. O-Ik is intercalated in Quaternary gravel deposits or overlying it, in the so-called Yamaya Formation, in the study area. This finding will be very helpful for clarifying the middle Pleistocene chronology and geomorphological development in both the mountain and foot areas across the Ou Backbone Range. It will contribute to setting a time scale for clarifying neotectonic movement and geomorphic evolution in Shinjo Basin through the middle Pleistocene.

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In this paper, we describe a series experiments undertaken to investigate how to determine materials for hammers used by stone age people in manufacturing stone tools. Examination of several attributes on experimental flakes detached with hammers of four different materials (hard stone, soft stone, antler, and wood), clarified that differences in hammer materials were best reflected in the attributes concerned with fracture-initiation area of the flake. Through combining these attributes, we established five types in this area that were strongly related to the hammer materials. By applying the Vickers Hardness measuring method to each of the hammers and experimental obsidian flakes, we made it clear that the five types were mutually connected with Vickers Hardness relativity between the hammer materials and the experimental flakes. Furthermore, we analyzed two groups of Upper Palaeolithic obsidian flakes from two sites in Southern Kanto, in terms of the five types established. The results of the analyses led us to suggest a high possibility that the flakes of both groups were mainly detached with soft stone hammers.

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Absolute ages of soils developed on the raised coral reef terraces in Kikai Island in the Ryukyus, Southwest Japan were estimated by using the mean rate of tectonic uplift and glacio-eustatic curve during late Quaternary in the previous paper. In order to estimate the soil age of other areas where the similar soils as those existed in Kikai Island were formed by using the index of soil age, which was highly correlated with some physico-chemical properties of soil itself, total iron (Fe_t), iron and aluminum extractable by dithionite-citrate (Fe_d, Al_d) and by acid ammonium oxalate (Fe_o, Al_o) were determined for all horizons of the six profiles in Kikai Island. The results obtained are as follows:
The crystallinity ratio of free iron oxides [(Fe_d-Fe_o)/Fe_t] gradually increased with the stage of soil development, while the activity ratio (Fe_o/Fe_d) decreased. There was a highly positive correlation between the soil age and (Fe_d-Fe_o)/Fe_t. By using this relationship, the ages of Minami-Daito Island soils, Lateritic Red soil and Lateritic Yellow soil whose age had not been determined, were estimated from the mean values of (Fe_d-Fe_o)/Fe_t, as 500±60 ka and 630±110ka, respectively. Therefore, it was concluded that the crystallinity ratio of free iron oxides could be a good index of the degree of soil development and age of Red-colored soils.

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