Multi-approach studies combining modal, heavy mineral and garnet analyses of sandstones have been carried out on the Late Cretaceous Terasoma Formation and the Palaeogene Otonashigawa Accretionary Sequence (AS) of the Shimanto Belt in the Kii Peninsula, Southwest Japan. Modal compositions of the Terasoma Formation change upward from feldspathic wacke to lithic wacke. Heavy mineral assemblages also change upward from the one rich in zircon and garnet with epidote, titanite and allanite to the one rich in euhedral zircon. The garnets from the Lower Member are mostly almandine, low and intermediate P/T types with minor high P/T type and grandite. In the Middle Member, the proportion of low P/T type increases at the expense of high P/T type and grandite garnets. These trends suggest that Coniacian violent felsic magmatism took place and their products thickly roofed the basement rocks. Modal compositions of the Haroku formation in the Otonashigawa AS change upward from lithic wacke to feldspathic arenite. The heavy mineral assemblages of the lower members are rich in zircon and garnet accompanied by allanite and greenish-brown hornblende. Sandstones of the uppermost member contain abundant epidote, allanite and titanite. The chemical compositions of detrital garnets also show a decreasing trend of the pyrope-rich almandine (intermediate P/T type garnet) and an increasing trend of spessartine-rich almandine (low P/T type garnet) from the lower to upper members. A few grandites were extracted from the uppermost horizon. These data suggest that felsic volcanic products and intermediate to high grade metamorphic rocks are the probable sources of the Otonashigawa AS. Due to the successive erosion, granitic, low P/T metamorphic rocks and calcareous metamorphic rocks were exposed to the surface. Roofing and unroofing processes are especially suggested by changes of the proportion of euhedral zircon, allanite, spessartine-rich almandine garnet (L), high P/T garnet and grandite garnet.

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Distribution and features of incised valleys and buried terraces in the Yodo River lowland, the Osaka Plain, Japan were reconstructed using a borehole database. Two gorges were discovered in the incised valley of the paleo Yodo River. The width of the incised valley was large in the lower reach of the river due to the effect of wave erosion. The buried terraces distributed intermittently along the paleo Yodo River were interpreted as river terraces based on their distribution and morphology. The River bed gradient of the paleo-Yodo River changed in the two gorges. The gradient in the upper reach of the gorge is gentle, whereas the lower reach is steep. This is ascribable to tectonic movement to form gorges and sedimentation and lateral erosion there. The older upper terraces have gentler gradients converge with the paleo Yodo River bed in the upper reach. The effect of river bed degradation associated with sea level fall seems to have progressed upstream.

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Varved sediments are very useful for studies attempting to clarify the high-resolution record of paleoenvironments, because they are expected to contain annual or sub-annual records of depositional environments. In order to obtain annual records such as annual thicknesses, color tones, and chemical compositions, at the very least, it is necessary to detect the boundaries of annual bands. Additionally, such detection and thickness measurements should be reproducible. The detection of boundaries and the measurement of thicknesses in varved sediments are commonly carried out by megascopic or image analyses. However, human error and difficulties in assessment of reproducibility often accompany megascopic measurements. On the other hand, photographs, soft X-ray images (X-ray radiographs), and the results of XRF mapping can be used for image analysis. Image analysis methods such as the peak detection method and wavelet analysis attempt to detect varve boundaries and measure varve number and sedimentation rate; however, some difficulties remain in these analyses, especially for recognizing varve boundaries. In addition, wavelet analysis has low resolution for detecting individual lamina boundaries, and waveform analyses such as the peak detection method are not suited for data containing high-frequency physical noise.
In this study, we applied a novel method for detecting lamina boundaries, especially in varved sediments, which is described by the following procedure: (1) smooth pixel values (gray value) of the lamina image, (2) map a maximum slope point of gray value in a square-shaped moving window (W1) on the image, (3) obtain a median gray value in a linear moving window (W2) along a stratigraphical section, and (4) detect lamina boundaries using a combination of the maximum slope point and the median value. An application of the lamina identification method of this study to a soft X-ray image of varved diatomite yielded a well-defined tricolored varve image and averaged transmittance value of soft X-rays in each lamina of the varve image. The thicknesses of varved sediments obtained using the tricolored image and the transmittance value of lamina can be easily converted into time series, and applied to spectral analyses.

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The Middle Pleistocene Hiruzenbara Formation, characterized by varved diatomite of a dammed lake deposit, is distributed in the Hiruzenbara Basin, Maniwa City, Okayama Prefecture. The varve consists of a set of light green and dark green laminae intercalating many sediment gravity flow deposits. In this study, we examined sedimentary facies of the sediment gravity flow deposits, and stratigraphical variation of these deposits and varve thickness. The results show that the varve thickness tends to increase upward, suggesting an increase in diatom production or size of diatom shells, and that the sediment gravity flow deposits can be classified into flood induced and slope failure induced types based on their sedimentary facies, lateral continuity and including diatom assemblages. The deposits of flood induced type show depositional properties of hyperpycnal and homopycnal or hypopycnal flow. Depositional frequency of the flood induced type is belived to be influenced by climatic environments. On the other hand, the slope failure induced type, suggesting deposition from sediment gravity flows triggered by lake slope failure, has rip-up clasts or is characterized by a structure less bed. Because the rip-up clasts in this type show ill-sorted size distributions, the proximal depositional environment near a slope base of the paleolake is suggested. The uppermost and lowermost parts in the analyzed section show lower frequency of the sediment gravity flow deposits of slope failure induced type whereas the lower part shows relatively high frequency of these deposits, with frequent slump scars.

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