Sources of non-glacial, loess-size quartz silt and the origins of 'desert loess' [Review]

摘要

Descriptions of peridesertic loess deposits and possible non-glacial origins for silt size quartz are reviewed, including direct release from weathered bedrock. Results from salt and frost weathering experiments are presented and methods by which sufficient energy can be imparted to sand size grains to release silt-size fragments are identified. These fragments may then be entrained by aeolian or fluvial action. Results from fluvial comminution experiments indicate that high energy, mixed sediment fluvial systems may be very effective in generating quartz silt. Purely aeolian attrition is also seen as a major source of silt size and finer material. Results from aeolian abrasion experiments performed using crushed quartz sand are complemented by trials using sands from deeply weathered granite and Pannonian Sands from Hungary. Field and laboratory observations are therefore seen to argue for the existence of deposits that can be classified as 'desert loess'. (C) 2002 Elsevier Science B.V. All rights reserved. [References: 166]