Grain-Size Characteristics of Sediment Transported During Dust Storms

Abstract

ABSTRACT The grain-size characteristics of sediment transported by wind in creep, saltation, and suspension during 15 dust storms in the Slims River Valley, Yukon Territory, were investigated. Grain-size analysis of the transported sediment indicated that the suspended sediment is significantly finer and better sorted than the sediment transported in either surface creep or saltation. The data also show that during dust storms the mean particle size of the suspended sediment decreases as a power function of height. The grain size distributions of the sediment transported in suspension and surface creep are characterized by strong positive skewness, which results from the selective removal of surface particles small enough to be transported by the wind at a given velocity. In contrast, the grai -size distribution of the saltation samples are negatively skewed, which is thought to result from the selective removal of the finer particles into suspension from those particles initially lifted from the surface into the air stream. Thus the proportion of sediment initially entrained into the air stream which returns to the surface in saltation will lack the fine grains removed in suspension and will therefore tend to be less positively or negatively skewed.