紀伊田辺平野における先・原史時代の遺跡立地とその古地理
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概要
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The Kii-tanabe plain, located on the south-western coast of the Kii-peninsula, is a small delta which has filled up the drowned valley of the Aizu river. In this plain, there are many prehistoric and protohistoric remains that can be fortuitously used in estimating the time and paleoenvironment of the alluvial deposits. The auther classified the alluvial surfaces from the viewpoint of landform evolution, and tried to reconstruct the paleogeography based on analysing the physiographic environment and the archeological data of the human remains. The results are as follows:The alluvial surfaces in this area can be divided into four surfaces: sand bar I, sand bar II, upper delta and lower delta. The paleogeography during prehistoric and protohistoric era had changed according to the steps outlined below.(1) By the earliest Jomon, Oshigatamon stage (around 8000yrs. B.P.), the sea invaded landward and the shoreline receded about 2km behind that of the present day.(2) With the progress of transgression, the embayment area spread over the Kiitanabe plain, and the blue-grey clay with shell was deposited on the bay-bottom.(3) On the open coast, the sand bar I was formed just after the sea-level reached its highest point during the middle Jomon period (around 4400yrs. B.P.), while as to the inland region, it became a lagoonal environment, and humic silt, silt, or peat was accumulated.(4) After slightly falling once, the relative sea-level rose slightly and the sand bar II was formed in front of the sand bar I. (probably around 2400yrs. B.P.)(5) A regression which attained more than 2m below the present sea-level during the Yayoi period and which had been known in other regions, caused dissection of the sand bar I, sand bar II and upper delta. The lower delta composed of fluvial sand and gravel was formed along the present river.
- 人文地理学会の論文