Experimental eolian abrasion of very fine grains at different atmospheric pressures

Quartz, orthoclase, magnetite, augite, and olivine, have been subjected to air-tunnel transport to assess the relative effects of eolian abrasion of very small grains of different minerals. Experiments were conducted at both high and low air pressures, with pressure and velocity values of approximately 1450 mb (1.4 atm), 22.5 m/sec, and 199 mb (0.2 atm), 9.3 m/sec, respectively, in partial preparation for returned Martian surface sample investigations. Results indicate that grains of such small size as to be generally carried in suspension are capable of eroding. No lower limit was found to the size of grains whose texture was modified by eolian transport, in contradiction to Kuenen (1960). Atmospheric "cushioning" effects are real, but do not impose a lower size limit for grains capable of eroding. Instead, they effect a decrease in rate of erosion of materials. The manner of textural modification in an eolian environment differs for different minerals, depending upon, and reflecting, the mechanical durability of those minerals. Durability or "survivability" of grains in transport environments cannot be predicted solely by the Moh's hardness of those grains. Sedimentological interpretations based on grain textures must take into account differences in rate and character of production of those textures for different minerals and grain sizes. Illustrations of air tunnel abrasion-induced surface textures of minerals are given for purposes of comparison with natural materials.