Desert Pavement Formation

Reg soils are closely associated with desertic regions. They have developed on stable surfaces where coarse, gravelly desert alluvium is exposed, and are characterized by a well-developed desert pavement and exhibit some well-defined soil horizons. They occur mostly on depositional surfaces where stones and gravels have been deposited since Neogene times. The surfaces commonly consist of stony, unconsolidated sedimentary deposits in which limestone, dolomite, chalk, flint and marl predominate, together with some fines (silt and clay). Sandstone and granite debris have also been reported to contribute to Reg formation. Less frequently, they form on sedimentary bedrock (Fig. 1.5). 

The result in terms of soil formation is a loss of soil. In desert areas covered by physically weathered shallow soils, deflation removes mainly the fine and medium-sized particles - clay and silt first, the somewhat coarser sand afterwards - and leaves behind a desert pavement, variously called reg (Sahara), serir (Libya) ox gibber plains (Australia). 

McFadden L.D., McDonald E.V., Wells S.G., Anderson K., Quade J., Forman S.L. The vesicular layer and carbonate collars of desert soils and pavements formation, age and relation to climate change. Geomorphology 1998 24 101-145. 

Wells et al. (1995) tested several competing models of desert stone pavement formation by comparing the He exposure ages of pavement clasts with those of basalt outcrops from which they were derived. They obtained identical ages, which they judged as clear evidence that clasts had remained at the surface continuously and were not concentrated randomly by processes such as surface runoff or upward migration within soils. 

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