Eolian sand bodies of the world

This chapter examines the eolian sand bodies of the world. Analyses regarding grain size and sorting distribution at Great Sand Dunes indicate that the higher dunes contain much more fine-grained sand and much less medium-grained sand than do the lower dunes, and, in addition, they are definitely better sorted. Cross-stratification in eolian deposits is the product of several distinct processes of transport. These processes are saltation or ripple migration that include various amounts of surface creep, grainfall (a dropping of grains from sand in suspension), and avalanching either by mass movement or by grain flowage which involves the downhill rolling or sliding of discrete particles. Penecontemporaneous deformational structures including various types of faults and folds, flames, break aparts, and rotated blocks are sufficiently numerous in most eolian deposits to serve as useful tools in determining genesis. These structures are good indicators of the nature of the stress and therefore provide information on the part of a sand body involved. Sufficient observations have been recorded to establish that the lee side (or slipface) of most modern dunes stands at 30° or slightly more and that the length of the foresets developed on it may be 8 or 10 m and often much more. © 1983, Elsevier Science & Technology. All rights reserved.