Abstract
The red weathering crusts appearing in Kitakami Massif, Northeast Japan were studied geomorphologically and stratigraphically, and the following results were obtained. 1. The red weathering crusts were generated mainly on hilly land and terrace in the margin of Kitakami Massif, but those were also observed partly on peneplane. 2. Because the red weathering crusts were covered with volcanic ash and secondarily deposited red weathering materials in general, the greater parts of the red weathering crusts were recognized as fossil soil, however some of those on hilly land were recognized as relic soil. 3. Judging from morphology and chemical properties of the red weathering crusts, those are similar to the zonal red soils in humid sub-tropical zone. Based on the stratigraphic relation, it is considered that those are not zonal red soils formed under recent bio-climatic condition, but paleo-red soils formed under past warmer bio-climatic one. 4. It is presumed that the volcanic ash layers appearing on peneplane of the northern part of Kitakami Massif, consist of typical volcanic ash stratigraphy, had been generated in Wurm glacial age. From the facts, it will be assumed that red weathering crusts in Kitakami Massif were formed under warmer bio-climatic condition before Wurm glacial age. Actually, based on the occurrence of red soils, Matsui (1962) has presumed that red weathering crusts were formed perhaps in Riss/Wurm interglacial age, and at that time the formation of red weathering crusts had been prevailed on the Pan-Japanese scale. 5. The writer has considered that the difference on the geological history may be existent between the northern half and the southern half of Kitakami Massif, during the dissected process of topography from the formation of red weathering crusts to the deposition of volcanic ash, from the deposited condition of volcanic ash layers and of secondarily deposited red weathering materials.
