Optically stimulated luminescence (OSL) is well known as “OSL dating” in the Quaternary chronological science field. On the basis of OSL intensities of a mineral grain in present sediments, we can judge whether the grain has been bleached or un-bleached during its transport process. We discuss the relationship between the percentage of bleached grains (bleaching percentage : BLP) in each sample and the transport process of fluvial sand grains. BLPs of alkali feldspar grains of active sand bar surface and flood deposits formed by typhoon No. 0423 (Typhoon Tokage) in autumn 2004 from two river systems in western Japan show that alkali feldspar grains are well bleached upstream and in tributaries where sand-gravel bars evolve on/near the water surface, while the grains are not easily bleached downstream where the channel is filled with water. Taking into account depositional environments, bar-channel deposits in braided-river systems and crevasse-splay deposits in flood plain systems may offer well-bleached fluvial samples which are suitable for OSL dating. By adapting an OSL technique to sedimentological investigations, sedimentological perspectives and OSL dating technique can complement each other.

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An IMAGES core MD01-2421 (45.83 m) from the northwest Pacific Ocean off central Japan yielded twenty-three tephra beds. Descriptions of the twenty-three tephra beds have been made using the major-element composition of glass shards and refractive indices (RI) of glass shards and phenocrysts. As a result, at least seven on-land maker tephra layers have been identified. Two tephras come from Kyushu : Aira and Aso calderas. Four tephras come from central Honshu : Mt. Akagi, Hakone caldera, Mt. Ontake, and Mt. Tateyama. One tephra, the lowest layer of all, comes from northeast Honshu : Numasawa caldera. During the process of identifying the tephra beds, it became clear that the RI of Ontake No.1 Pumice (On-Pm1) at Suruga-Oyama (type locality), derived from Mt. Ontake, changed gradually during its eruption, and the RI of glass shards (1.503-1.506) in the middle to the top portion of the fall units was higher than the RI (1.501-1.503) in the lower unit, known as its type value. Furthermore, an age model for MD01-2421 was constructed by means of the oxygen isotopic stratigraphy of the benthic foraminifera (SPECMAP age : Martinson et al., 1987), using 12 calendar ages of foraminiferal fossils calculated from the accelerator mass spectrometry (AMS) ¹⁴C ages (younger than 44 ka) and AT tephra (Oba et al., 2006). This sedimentary core covers the last 144,000 years. The eruptive age of each tephra bed in this core and its error included in each SPECMAP age can be estimated from this age model. Akagi-Kanuma tephra (Ag-KP) is one of the marker tephra beds in the north Kanto Plain, and is 44.2±4.5 ka. Hakone-Tokyo (Hk-TP) tephra covers the south Kanto Plain, and is 66.0±5.5ka. Aso-4 tephra is 87.1±6.7 ka. We estimate the eruptive age of Ontake No.1 Pumice (On-Pm1), which lies just above the marine terrace surface and is regarded as having formed during MIS 5.3 in the south Kanto Plain, as 95.7±5.3 ka. The stratigraphic position of On-Pm1 in the oxygen isotopic stratigraphy agrees with geomorphologic evidence. Tateyama D tephra (Tt-D) derived from Mt. Tateyama in the Hida Mountains, central Japan, is 98.9±3.5 ka. Numazawa-Tagashira tephra (Nm-Tg) is described in the north Kanto Plain, and its stratigraphic evidence, estimated from shoreline sediments, matches the eruptive age of 129±3.0 ka of this study. This is the first time the stratigraphic relationship among these several tephra beds has been documented in a single section with a continuous and precise oxygen isotopic stratigraphy.

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In order to determine the absolute dates of the pottery types during the Late and Final Jomon periods in the area surrounding the Noto Peninsula, and to consider the origin of charred residues on the pottery, the authors examined ¹⁴C dates, carbon and nitrogen stable isotopes and C/N ratios of the charred residues and lacquer-coats on potteries excavated at Okyozuka site, Ishikawa, Japan. Carbon and nitrogen stable isotope analysis and C/N ratios have revealed that all of the food residues collected from the inner surface of potsherds during the Late Jomon period seem to be derived from animal protein, and some of these food residues seem to be affected by marine reservoir effect. On the other hand, the Final Jomon potteries showed normal values of the isotope values and C/N ratios, and ¹⁴C results were consistent with those of surrounding areas. These ¹⁴C dates of Final Jomon potteries were calibrated using IntCal04 calibration curve. The results show consistent correlation between ¹⁴C dates and pottery type sequences : Nakaya type is placed ca. 3,200-2,850 cal BP (1,250-900 cal BC), Shimono type is ca. 2,950-2,800 cal BP (1,000-850 cal BC), and Nagatake type is ca. 2,750-2,650 cal BP (800-700 cal BC).

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The depositional age of gravel bed at Sebadani, in the upper reaches of Azusa River at the Hida Mountain Range, has been determined by AMS ¹⁴C dating. We measured four new AMS ¹⁴C datings of wood fossils in the gravel bed of Sebadani. The previous study estimated that the formation age of the gravel bed is 70,000-50,000 yrs BP, which corresponds to marine isotope stage (MIS) 4. However, the new obtained ages were ca. 48 ka BP from the wood fossils in the gravel bed.

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