“Desert” loess versus “glacial” loess: quartz silt formation, source areas and sediment pathways in the formation of loess deposits

Pathways are presented, which show the proposed sequence of events involved in the formation of loess deposits, both hypothetical deposits and those of central China, Hungary, Nigeria and Tunisia. These pathways illustrate the potential role of, and inter-relationships between, a variety of silt generating mechanisms in the formation of loess. Using these pathways, the existence of “desert loess” is discussed and it is concluded that this depends on how the terms “glacial loess” and “desert loess” are applied. If “desert loess” is taken either to signify “nonglacial” mechanisms of silt production or to characterise the environment from which aeolian entrainment took place, then “desert loess” is a very real and widely distributed deposit. However, if the term “glacial loess” is used to refer to the global climatic regime under which the loess deposit has formed rather than the geomorphic mechanisms responsible for silt generation, then “desert loess” would not be an appropriate term for the classification of loess deposits. It is suggested that classifying loess deposits with reference to the global climatic regime under which they accumulated would facilitate a greater understanding of the role of environmental conditions at all stages in the formation of loess deposits.