Abstract
The morphological, physical, chemical and mineralogical properties of Red-yellow soils (paleo-Red soils) in southern Kyushu were investigated, and the forming period of these soils was deduced from the relationship between distribution pattern and geomorphic history. The results obtained were as follows : 1. In the Miyazaki Plain, the Izumi Plain and Tanegashima, the distribution of the paleo-Red soils was limited to the old aged geomorphic surface, such as the higher terrace and the hilly terrain. On the higher terrace, the paleo-Red soils were buried under the brown loam layer in the Miyazaki Plain and Tanegashima. 2. The paleo-Red soils were characterized by high clay content, low organic carbon content, and, except for the buried portions, low base saturation of cation exchange capacity (CEC). The clay mineral composition included mainly kaolin mineral, the value of CEC per clay was low. The free iron oxides had an activity ratio of less than 0.4 and a crystallinity ratio of more than 0.5. These values ranged within those of the paleo-Red soils in other areas of Japan. 3. To estimate the formation period of the paleo-Red soils based upon the latest data on the landform evolution, it was clarified that the paleo-Red soils were formed from 400-500 to 110-130 ka.
