In the circumference of the Ôsaka region, there are widely distributed Plio-Pleistocene deposits, the Ôsaka group. In September of 1964, nearly complete, but without some limbs and tail bones, skeletons of a fossil crocodile were excavated from the upper part of the Ôsaka group, at the ground of the Ôsaka University, Machikaneyama, Shibahara, Toyonaka City, Ôsaka Pref.. The horizon was the fresh water sandy clay bed which lay between the 8th marine clay above and the 7th marine clay below, of that group. Thus, the geological age of this horizon is estimated to be the Early Pleistocene. It was the first discovery of the crocodile fossil in Japan, and then, this long snout crocodile was named as Tomistoma machikanense Kamei et Matsumoto (n. sp.).
This study is based on the data of some wells for exploration of oil and gas and the data of many shot holes for seismic survey. As a result of it, the Quaternary sediments developed in this area have been stratigraphically subdivided as follows: thickness A4: Bottom deposits of the present sea ? A3: Sand and gravel 10m± A2: Clay, peat and pumice 30m± A1: Gravel, sand, clay and peat 30m± S:Shikotsu volcanics (20, 000years B. P.) Shishinai Formation 50m± Nopporo Formation 50m± Characteristic change in distribution and arrangement of the Quaternary sediments in this area is thought to be due to three types of vertical movements, which differ distinctly with each other.
Several terrace levels may be observed in the coastal area from Matsusaka to Ise in the south-central part of Mie Prefecture. These are primarily made up of deposits of fluvial gravel less than 30 meters thick with lenticular layers of sand and silt, and may be grouped into three terrace surfaces, i. e., the lower surface, the middle surface and the upper surface. The flat surfaces of the lower terraces are in a much better state of preservation than those of the upper terraces, and to date marine formations have not been discovered in any of the terrace deposits. In addition there is an erosion surface corresponding to the “Age” erosion surface which has developed in the Tsu area of the north-central part of Mie Prefecture. This surface covers the upper part of the hills with the exception of only their very tops. The distribution and stratigraphic subdivision of these surfaces are shown respectively in Fig. 1 and Table. 1. A few explanations regarding the texture of the deposits and some estimations regarding the geological structure were made in this paper; however, a more complete report shall be made in the future.