Marine terraces in Noto Peninsula on the Japan Sea side of the central Japan were investigated with special reference to their geomorphic history and tectonic movements during the middle to late Pleistocene(Fig. 1). A large part of Noto Peninsula consists of a flight of marine terraces which have been classified into four groups, T, H, M and L in descending order of the elevation. The T terraces are further subdivided into T1 to T7, H into H 1 to H4 and M into M 1 to M3 (Figs. 2-8). The T terraces are very dissected, but their original surfaces are preserved as narrow flat tops of accordant heights which occupy extensive area of the inland of the peninsula. The H terraces surrounding the T terraces are continuously distributed, although they are smaller than the latter of width. The M1 terrace has the most well-preserved original surface consisting of thick marine sediments burying irregular bedrock reliefs at some places and is continuously developed throughout the study area. Thus, the Ml terrace can be correlated with the marine terrace formed ca. 120, 000-130, 000 y. B. P. during the Last interglacial transgression. It is inferred, therefore, that the formation of the oldest terrace (T group )of this area could go back to the early-middle Pleistocene and that the marine terraces would be resulted from a combined effect of continuous uplifts and eustatic changes of sea-level. Paleogeography of the three stages during the middle to late Pleistocene is reconstructed on the basis of marine terrace distribution (Fig. 9). It is obvious that progrssive emergence have occurred since the middle Pleistocene.
The elevations of former shorelines of the Ml terrace range from 110 m (an average apparent rate of uplift ca. 1 m/l, 000 years) at the northernmost part to 20 m at the southeast, indicating marked southward tilting with a small component of eastward tilting. However, examing trends of the terrace heights in detail, the Noto Peninsula is not a single tilted block, but consists of several small blocks, each showing southward tilting (Fig. 10). The boundary of each block coincides with that of the mountains. Noticeable tilting, however, should have started after the M1 terrace formation, judging from the fact that there is no significant difference in the gradient of tilting between the M l terrace and the higher ones. Southward tilting seems to have continued to the present. In addition, many active reverse fault dislocating the marine terraces of various ages have contributed to the fragmentation of Noto Peninsula into smaller blocks.

View full abstract

In Japan, most of rivers on alluvial fans are bounded by the artificial levees, which may affect or change fluvial processes of the rivers. In order to properly analyze the present stages in the development of alluvial fans, it is necessary to know differences of fluvial characteristics before and after building artificial levees.
Assuming that a present river bed shows the present fluvial characteristics and the other part of the fan surfaces shows the former fluvial characteristics before building artificial levees, low-water channel patterns were investigated using airphotos and the maximum grain sizes of fan deposits were measured in the field on Oi, Tetori, Kurobe, and Joganji alluvial fans in the central Japan.
Low-water channels on the present river beds show a braided pattern, and have directions of the flows along the artificial levees. The former low-water channels before the build of artificial levees, shown on the fan surfaces, also have a braided pattern and their main directions of the flows are radial from the fan apex (Fig. 1). Comparing the present low-water channels with the older, the former has a larger sinuosity than the latter. Intersect-ing angles of the low-water channels show the same tendency (Table 1).
At the same distances from the fan apexes, the maximum grain sizes on the present river beds are larger than those on the other part of the fan surfaces or the former river beds (Fig. 2).
These differences might come from the changes of river conditions or fluvial processes. In this study, examined are the three possible causes, that is, basin transitions by forest cuttings or landslides, artificial reformations of the river beds, and boundings of rivers by artificial levees.
After due considerations, the author concluded that the main cause of changing the flu-vial characteristics was the builds of artificial levees or fixing of river channels. Because the artificial levees bound the course of flows, the river can not completely adjust their morphologies or fluvial characteristics under given conditions. Especially under a flood with a given volume, flood flows may be concentrated in the present river bed by artificial levees and the velocity of the flood or the tractive force may be much higher than that in the river bed without artificial levees.
This study indicates that effects of artificial levees can not be neglected in order to analyze processes of alluvial fan formation or histories of alluvial fan development in Japan with considering the present river processes.

View full abstract