To clarify the stratigraphy of the denudation surfaces in the Abukuma Highlands, the author described the relation between the erosion surfaces and the superficial sediments formed during the Lower Miocene and the Plio-Pleistocene.
The following three groups of denudation surfaces were recognized in the Abukuma Highlands: the Higher surfaces which are 750 to 1, 050m. a. s. l., the Middle surfaces 550 to 730 meters in height, and the Lower surfaces 300 to 550 methers. The erosion surfaces are regarded as of subaerial denudational origin.
The lowest Miocene fluvio-marine sediments in the northern part of the study area are distributed along the fossil valleys cutting into the Higher-level erosion surfaces. The sediments are covered with the lower Miocene volcaniclastic rocks. The Plio-Pleistocene fluvial sediments and the pyroclastic flow deposits in the western margin of the highlands are distributed along the former river channels cut into the Lower-level erosion surfaces.
While the lowest Miocene series had been piled up, their hinterland had kept low relief. It was interpreted on the basis that most of the lowest Miocene strata were made up of sand to cobble, and were well graded and classified, and that the highest level of the Lowest Miocene was lower than the Higher level erosion surfaces. The relationship between the facies of the lowest Miocene sediments and the paleoform suggests that the low relief surfaces had been dissected by the fossil valleys. Thus, the age of the Higher-level erosion surfaces is prior to the Neogene subperiod. The Middle-level erosion surfaces truncate the lowest and the lower Miocene strata. And the distribution of the Middle surfaces doesn't overlap with the area which has the post-Miocene sediments. These paleoforms mean that the Middle surfaces were already been cut in the Pliocene. Therefore, the Middle-level erosion surfaces were formed during the Miocene epoch. The Lower-level erosion surfaces are unrelated the before-Pliocene structures, and are dissected by the fossil valleys which were formed in the Plio-Pleistocene boundary. The Lowerlevel erosion surfaces thus were considered to have feen formed in the Pliocene. The relationship between the development of denudation surfaces and the geotectonic history around the Abukuma Highlands suggests that the stages of denudation surfaces development are accord with ages of higher sea-level in millions years order. Moreover the denudation stages correspond with the ages of tectonic stability around the study area.

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During from 1957 to 1990, we saw some important changes in the process of large housing estate development in Sendai metropolitan area. The local private companies who were major developers in this area in 1960s were replaced successively by nation-wide private companies and then by land reclamation organizations. The developments were concentrated in the northern part of this region till the mid-seventies, but after that, they were dispersed throughout the region. The portions of areas which was devoted to housing whithin the newly developed land were sixty to eighty percent before 1973, decreased to between forty and sixty percent until the nineteeneighties. This study aims to explain the reasons for these changes by looking at the housing estate developement process as an economic activity.
Firstly, examining a few studies of real estate capital circulation leads us to certain principles of private-developer's housing development. In the land-purchase process, private developers have to try to purchase cheaper and larger lands for development. In the development process, they have to try design the developments so as to reduce developement costs, and at the same time, in order to generate more profit, they must try to increase the value of the housing land by arranging certain types of facilities for the people who will live there. Furthermore, they try to make cleen the identities of their housing lands so as to sell them as soon as possible and so as to maximize their profits in the sales process.
Secondly, the interaction between these abstract principles and some actual conditions was studies. It was found that the some unofficial guidances by municipalities favor the large nationwide private developers, while they increase their development costs. Furthemore, the rise of cost accelerates individualization of each developing area, because the companies have to sell them as soon as possible. This individualization, in turn, increases development costs even more. Of course, private developers seek to avoid increasing their costs. They intend to achieve this by attracting facilities to each developing area, by using facilities located outside each developing area and by receiving all sorts of public support. In the second technique, lands for development are limited to the areas near already developed areas or some facilities. It is difficult for private developers to develop such area, because of existing land-use, high land prices and so on. In such cases, developers resort to land reclamation plan.
Lastly, based on these principles of private developer housing development and the interaction of those principles with actual conditions, as discussed above, the process of the housing estate development in the Sendai metropolitan area is examined, taking topography, historical conditions, goverment policies and so on into account. It is concluded that the changes that were shown at the beginning of this abstract can be explained by the economic principles of private developer housing development, although topography, goverment policies and so on may retard or accelerate these changes. In other words, the activities of private developers make the features in this process.

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