抄録
Little has been worked on history of slope denudation under environmental changes of late Quaternary in humid temperate area like Japanese Islands.
We gave it general consideration of the history of local geomorphic environments and hillslope instability based on micro landform classification (Fig. 2), and analyses of sediments located in isolated small basin, called Kawadoi basin, Yamagata Prefecture.
Slope deposits are often interbeded with peat layers in the lowland and the peat layers provide adequate materials for pollen analyses and radiocarbon datings which enable to establish chronology of environmental changes. So there are close relationships between micro landforms and vegetation, that hillslope instability in the past also will be guessed by the fluctuations of pollen diagram. The main results are as follows;
1. Several periods of hillslope instability are identified by the analyses of cross sections (Figs. 3 and 4), i. e.
1) 46, 000-37, 000yr B. P., 2) 29, 000-27, 500yr B. P.
3) 27, 000-12, 500yr B. P. including the especially large sediment yield period at the age of 27, 000yr B. P., 4) 11, 000-8, 700yr B. P., 5) about 6, 000yr B. P., and 6) after 3, 000yr B. P..
2. On the basis of pollen diagram, the sediment is into four local pollen assemblage zones (MG, FG, L and R) including 12 sub-zones (Fig. 6 and p. 30).
3. Sediments yield periods are contemporal with the phase of changes of climate such as coldward age, warmward age and the Hypsithermal.
4. The Extra local pollen and Local pollen such as Betula, Carpinus, Zelkova and Ulmus, Fraxinus, Juglans and Pterocarya stands on the unstable slopes. These pollen are well included in inorganic horizons.
