The Sagami group, the lower Pleistocene deposit, distributes into the South Yokohama Hills, Sagamino Upland, and Oiso Hills in the southern Kanto region. The stratigraphy and sedimentation of the group in those aeas have been re-examined, and it has been known that the development of the Sagami sedimentary basin has the following three stages. 1. After folding in the Miura group, the initial subsidence of the Sagami sedimentary basin began, and a part of the rugged land surface was covered by a rush marine transgression. Thus the Naganuma and Ninomiya formations deposited. 2. Thereafter the basin spread with the progress of the basin-forming movement, while the regressive facies remained there, and volcanism began to the western district. The estuarine Byõbugaura and lacustrine Tsuchizaw a formations deposited overlapping the Naganuma and Ninomiya formations respectively. 3. Towards the end of the deposition of the Byõbugaura-Tsuchizawa formations a large quantity of volcanic ashes and lapilli (Tama Loam member) was supplied and the tectonic movement occurred in the Oiso Hills. In the meantime the Sagami sedimentary basin emerged in the whole area and the basin became extinct.
The site is located on a hill standing on the eastern shore of Lake Suwa, at the height of 880 meters above sea level (120 meters above lake surface). Stone artifacts and flakes were abundantly discovered in June, 1949, in the course of some house building construction. The greater part of the materials were collected at that time. Later in October, 1953, a test excavation was carried out, since it was supposed by Mr. Chosuke Serizawa that they might belong to the Pre-ceramic stage of culture. By the stratigraphical examination, it was confrmed that the stone tools were contained in the loam layer, while the ceramic fragments of Early Jomon Period were found in the upper humus layer. Thus the stone artifacts and flakes of Kita-odoriba found in 1949 were evidently attributed to the Pre-cramic Culture. Most of the stone tools are shaped in laurel leaf or willow leaf point, with the exception of a handful of side- and end-scrapers, drills and utilized flakes. A presumable graver was found together (Fig. 3-11). They are mostly made of obsidian, but scarecely of slate. These specimens are particularly convenient for the analysis of tool making process. The materials for points can be devided into three types. Type 1 is a nodule itself, from which a pointed tool is directly trimmed. Type 2 is a flake removed from the nodule. In this case, a flake is retouched into a point. Type 3 is a peculiar flake“d”(Fig. 4. 5), which is produced in the course of tool making from the materials of Type 1 and 2. This applies correspondently to the other tools than points. Some artifacts, however, are so perfectly retouched as to retain no trace of the original form, and these are treated separately. Tools of Type 1-3 are analysed in view of manufacturing process. The points of this site are mostly bifaced or semi-bifaced. They are generally small (approximately 5cm. in length) with the exception of two large ones (12-15cm.) Point industries, which are generally characterized by small and abundant points, have been found so far in the Central Region, at Ueno-daira, Yashima, Babadaira, Koyashiki, etc., and in the Kanto Region, at Mitsuya, Motojuku, Takei, etc. These industries are reasonably dated back to the Upper Pleistocene, but many important questions are still open. For their relations with some of the knife industries, as well as the problem of their chronological subdivision are not yet clear. In near future, the author intends to clalify the reason why the three different types of materials exist in the same industry.