The existence of paleo-lake basins in the so-called “Green-tuff Region” of northeastern Japan, has been pointed out by N. Kitamura (1959), and by K. Mitanl (1964). It is said that most of these paleo-lake basins were formed by the intensive crustal movements during Miocene and Pliocene times.
The present author assumes that there has been a close relationship between the existence of such paleo-lake basins and the Pleistocene volcanisms ; the present landforms have been influenced directly by the crustal movements and the volcanisms. And so, it is very necessary and important for the author to clarify the geomorphological development of these paleo-lake basin area in the volcanic region.
In this paper, the author took the Narugo Basin, one of the paleo-lake basins mentioned above, in order to clarify the influences of the geotectonic movements and of the volcanisms, and he tried to analyse the formation of the topographical characteristics in the basin and it's vicinity.
The results are summarized as follows:
1) The Narugo Basin was formed by the combination and the repetition of crustal movements in late Tertiary and early Quaternary, and the violent volcanisms such as the explosion of the vast pyroclastic deposits (Pleistocene Uwahara Dacites), spread over the eastern part of the basin fringe. These volcanisms seem to have been guided by the pre-existing active tectonic lines (Some of these are named “Honjo-Matsushima Geotectonic Line” by Oide and Onuma, 1960). Therefore, the present author assumes the formation of the present Narugo Basin to be a “volcano-tectonic depression (Williams, H. 1941)”.
2) The Narugo lacustrine sediments were deposited in the Narugo Paleo-Lake which was formed by the above mentioned movements. Theses sediments can be classified into two ; loose conglomerate and sand beds of the marginal f acies, and well laminated tuff aceous siltstone and sandstone beds of the central f acies. They imply former violent dacitic volcanism.
3) After several upheavals of the whole region, several levels of erosional surfaces and fluvial terrace surfaces were formed ; in late Pleistocene, the Narugo Paleo-Lake became shallow due to the progressive accumulation of fluvial deposits and the upheaval of the whole region. Soon after, the Eai Paleo-River began to incise itself into the bottom of the basin, which formed the Sanjo Surface (the first terrace), and the Narugo Paleo-Lake disappeared.
4) The Narugo Volcano, situated in the west center of the basin, started it's activity under fluviatile-lake environments and formed tholoide to aspire type volcanoes. This volcanic activity continued until the formation of the Daigakunojo Surface (the second terrace).
5) It is inferred from the character of the deposits, their distribution, and the inclination of the Sanjo Surface, that there were comparatively new geotectonic movements during and after the formation of the terrace surface. The author assumes the existence of the “Nuruyu-Nagashida Geotectonic Line” for the central axisis of these movements. The western part divided by this geotectonic line, shows on elevating tendency, while the eastern part shows a subsiding tendency.
6) Judging from the character of the deposits (including peaty materials) and the longitudinal profile of the Daigakunojo Surface, which submerges under the alluvial surface outside the basin, it seemes to have been formed during or soon after the Würm Ice Age.

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The purpose of this paper is to depict the detailed distribution of surface wind over central Japan in consideration of the pressure patterns in the winter seasons. The distribution of surface wind on a local scale is affected not only by the flow pattern of the synoptic scale, but by local circulation, such as land and sea breezes, as a result of diurnal variations in the local pressure pattern. Generally speaking, as the latter is superimposed on the former, the wind distribution is more complicated on a local scale. In the winter season, however, a severe winter monsoon prevails over Japan and adjacent areas, while the local circulation is relatively weak, then the detailed distribution of surface wind is mainly influenced by flow patterns resulting from the winter monsoon. Invasions of the sea breeze are restricted to within a zone of approximately 15 kilometers from sea-coast and the alternation from land breeze to sea breeze occurs after 10 a. m., as shown in Fig. 3, in the area of Pacific sea-coast where the sea breeze is established during this season.
Available data to reveal the detailed distribution of surface winds at optional times are so sparse that the data of climatological stations, where observations are made at 9 a. m. only, were mainly used in this study.
First of all, one hundred sheets of daily maps of stream-lines of surface winds were drawn, using the data of 623 stations in this region. These maps show that the characteristic distribution of local wind systems is apparently perceived in relation to a gradient flow pattern, which is decided from synoptic weather maps at that time. Then the gradient flow pattern over central Japan, corresponding to the distribution of surface wind systems, was classified into 6 types as follows.
Type I Gradient wind over this area exceeds 10m/sec and comes from 250° to 330°. (Wind direction represents angle measured clockwise from north.)
Type II Gradient wind speed is the same as Type I. Gradient wind direction is included in the fanshaped domain from 330° to 20°. Curvature of isobars is cyclonic.
Type III Same as Type II, but curvature of isobars is anticyclonic.
Type IV Gradient wind speed is the same as the above, but its direction is between 30° and 60°.
Type H Winter monsoon weakens and gradient wind speed lies below 10m/sec.
Type FL Trough accompanied with cyclone and front affects the wind distribution on this area.
The frequency of flow patterns is listed on Table 1.
As shown in Table 2, transition of flow patterns prevails in the following order.
(1) I—II—III—H—FL
(2) IV—(III)—(H)—FL
Case (1) is an ordinary cycle of the seouence of pressure patterns in winter season. As soon as a major through passes over Japan, a severe winter monsoon breaks out in this area and the flow pattern shows Type I or II. On the other hand, case (2) appears when the Siberian High moves to the northeastern part of Shiberian Continent.
In the case of Type H and FL, the wind distribution is too intricate to deal with in this paper. Briefly speaking, in Type H a gentle pressure gradient leads to an unsystematic distribution of local wind, while in Type FL, the wind distribution is extremely different in each case. These two types are excluded from thie paper.
Data of wind for the remaining types were arranged into the windrose, related to each of the flow patterns, for each of the meteorological stations. Fig. 5 illustrates an example of regional characterisitics of the windrose for Type IV in the Kanto plain. The prevailing wind direction is evident for most stations, though in certain parts of this area the prevailing frequency is absent and indistinct, where either a convergence line is formed between local wind systems or topography influences the wind direction in mountainous areas.

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It has long been believed by many geographers in Japan that the Tenryu River beheaded the Toyo River along its middle course near Nakappe town, and then the Ochise River, a tributary of the former, encroached through the wind gap into a fossil valley of the previous main stream of the latter, having remained a valley watershed (Talw asserscheide in German) at Ikeba village. This valley watersched has a length of about 500 meters, sloping gently to eastward. Its west end is terminated by the valley-head of the Shimano-kawa, one of the source streams of the present Toyo River ; and the eastern margin slopes gently into the stream of Tero-sawa, one of the source streams of the Ochise River in the Tenryu drainage basin, forming several alluvial cones.
Through his observations, the writer cannot approve of the opinion of stream-piracy above mentioned. The reasons are as follows:—
1) The breadth of the Ikeba valley watershed is too narrow to assume that it was the previous main stream of the Toyo River.
2) Both sides of the valley watershed show concave slopes with no terrace landforms.
3) The outcrops along the valley floor are all composed of angular and ill-sorted talus deposits without water worn gravels.
So the Ikeba valley watershed cannot be assumed to be the fossil valley of the Toyo River. On one hand, some geologists presumed a fault-line along this valley watershed, the pioneer of whom was B. Naumann, who found the “Medianlinie”, the main geotectonic line in southwestern Japan. Though the writer could not find any actual evidence of a fault, it is rather probable that the valley watershed here was originally formed as a fault valley.

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