Studies of the Kwanto Loam

Abstract

The patterns of sedimentation, grain size, and roundness, and mineralogical composition of the Kwanto loam in Shimosa terrace land, Chiba prefecture, Japan were studied., The Kwatno loam is stratified upon the sandy gravel bed which lies on the Narita formation, and mainly consists of rock fragments of weathered basic tuff., The Kwanto loam is classified into two groups, the upper and the lower A pumice bed lies about 20 cm above the bottom of the upper Kwanto loam (Fig., 1)., The mean grain size of the upper Kwanto loam by weight percentage is bout 3., 6∼3., 8 Phi in diameter while the lower Kwanto loam is 2., 8∼3., 2 Phi., The variation in grain size in the upper Kwanto loam is far less than in the lower (Table 2)., The frequency polygons in Fig., 3 show the difference between the upper and lower., The roundness in the upper Kwanto loam varies from 0., 20 to 0., 22 while in the lower from 0., 33 to 0., 37 (Fig., 5)., The two loams can be distinguished fairly well by their mineralogical composition., The upper Kwanto loam rich in mafic minerals, such as olivine and pyroxene, while the lower is rich in felsic minerals (Table 3)., From the evidence just mentioned, it may be inferred that the upper Kwanto loam is aeolian while the lower is aqueous, and there is a time interval of sedimentation between these two loams.,