熊野浦沿岸の海岸段丘と古土石流堆積物

抄録

The previously circulated views on the stratigraphy of terrace deposits along the southeastern coast of the Kii peninsula are amended and the periods of slope instability in the same area are discussed in this paper.
Sequence of coastal terraces with stratigraphy of terrace deposits is summarized in Fig. 6. Sealevel change including crustal movement, which may be continuous uplift with tilting to the north, as shown in Fig. 7 is derived from the sequence. Three major transgressions in the middle and late Pleistocene are noticeable. The Shingu Gravel indicates the development of alluvial fan in the age just prior to the maximum of the regression which precedes the transgression exhibited with the Kumanoura formation.
Old debris-flow deposits are laid on a part of dissected piedmont gentle slopes and colluvio-fluvial deposits fill small valleys dissecting the terraces. Stratigraphic relation of such slope deposits to terrace deposits suggests the periods when a lot of slope deposits are produced, namely the periods of slope instability. Increase of fluvial deposits as the Shingu Gravel may also reflect such a condition. The periods of slope instability in the area seem to coincide with the ages of low sealevel.