MORPHOLOGICAL PROPERTIES OF EOLIAN SAND GRAINS

Abstract

Kuenen and Margolis recognized frosting on the quartz sand grains as the result of mechanical and chemical process that were active in the eolian environment. On the contrary, Cailleux, Ottoman and Kosugi recognized it as the result of wind abrasion. On the basis of Cailleux, Ottoman and Kosugi's view, the writer reports the results of some measurements of the quartz sand grains and discusses them in this paper. Approximately 82, 800 samples were collected from eight environments in Pleistocene and Holocene : offshore, foreshore, backshore, dunes I, II, III, inland dune, eolian sands beneath a black humus soils, and eolian sands of lower Pleistocene in western Japan and Antarctica. The length of quartz sand grains studied ranges from 0.35 to 0.71mm. Observations were made by the binocular microscope with canadabalsam on a green background. Magnification is x 60 for the 0.71mm grains, and x 75 for the 0.5 and 0.35mm grains. Among the quartz grains, four main types may be distinguished. 1) angular shiny grain (AS) 2) round shiny grain (RS) 3) semi dull grain (SD) 4) round dull grain (RD) The results obtained may be summarized as follows: 1) Prevailing sand grains of RD type are observed in the eolian sand beds. In contrast to the eolian sands, the beach sands contain a high percentage of AS and RS type sand grains. 2) In the Holocene eolian sands, dune III sands contain relatively high percentage of sand grains of RD type (17 to 66 per cent). On the other hand, in the dune I sands, the percentage of sand grains of RD type is as low as 1 to 19. This is shown Figure 2. 3) Correlation of the thickness (t) and the percentage of sand grains of RD type (A) of dune III sands is shown to be A=0.878t+13, 188. This is shown in Figure 3. 4) In Wright valley, Antarctica, the migrating eolian sands contain higher percentage (76 per cent) of sand grains of RD type than in Japan. 5) In the pleistocene eolian sands, Tanegashima D3 sand and Hojyo eolian sand beds contain a high percentage of the RD type sand grains. Its properties differ greatly from Holocene eolian sands.