1989 Volume 43 Issue 6 Pages 354-365
The clue to and an advance in study of the Nohbi Tilting Basin has a social background of problems caused by landsubsidence in the Nohbi Plain. The Nohbi Tilting Block, a crustal block including the Nohbi Plain in the west to Mt. Sanage in the east, is characterized by Quaternary tilting movement (Figs. 1 & 2). The Nohbi Tilting Basin, which occupies a western half of the Nohbi Tilting Block, was formed by the Nohbi Tilting Block Movement, and is filled with the Quaternary Owari Group. Accompanied with progress of the tilting, the Owari Group was deposited under the control of glacio-eustacy, and is composed of alternating marine sediments during transgression and fluviatile ones during regression (Figs. 4 & 5). Topography of the Nohbi Tilting Block consists of Alluvial plain, uplands (terraces), hills and mountains toward the east (Fig. 3). The western margin is bounded linearly by the Yoro-Ise Bay Fault (Fig. 2). Rivers flowing within the tilted block tend to converge to the western margin (Fig. 3). In the Nohbi Tilting Basin, Quaternary formations related to the tilting dip westwards as a whole. Among these formations, older one inclines with a larger dip, and most of them become thicker and deeper toward the west (Figs. 5 & 6). The estimated rates of the tilting tend to have become larger in younger stage (Table 1). The Nohbi Tilting Block constitutes a part of the Chubu Tilting Block, which is a larger crustal block bounded by the Itoigawa-Shizuoka Tectonic Line on the east and the Tsuruga Bay-Ise Bay Line on the west. The Chubu Tilting Block Movement is a large scaled tilting movement mainly in the Quaternary. Major relief of the eastern part of Southwest Japan is characterized by the morphology of undulation trending in a NNE-SSW direction (Fig. 7). The undulated relief is longer in the western slope and shorter in the east, and is about 80 km in wavelength. Accordingly, the tiltings correspond to movements in the western slope of the undulated relief. Quaternary sedimentary basins such as the Nohbi Tilting Basin have been formed where the trough of Quaternary undulation superimposes on the Neogene sedimentary provinces stretching sub-parallel with the elongation of Southwest Japan.
