ABSTRACT

Some loess is produced by direct glacial action. This is a two stage process: the fine quartz which forms the bulk of the loess is produced first as sand-size grains, and then these grains are crushed. The glacial crushing action tends to produce a wide range of particle sizes with concentrations in the sand-size range and the <200µ range; this product can be divided into two types of deposit, sand and loess. Quartz particles of about 80µ diameter are most easily raised by the wind and carried in suspension. Loess in deposits has a high tensile strength and forms vertical structures because the interparticle Van der Waals forces are of the same order of magnitude as the weight of the particles. Six events define the history of a loess deposit: two stages in the formatio of the material, transport by glacier, deposition, transport by the wind, and deposition again. Each of these events is important and affects the eventual nature of the deposit. The aeolian transportation process is quick and efficient, and the formation of the loess deposit can be correlated with the retreat of the glacier which produced the necessary detritus.