Desert alluvium

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). 

Tlhe Sedan thermonuclear detonation in July 1962 created the largest A man-made crater ever produced by a single explosive. Approximately 7.6 million tons of earth were moved by this detonation to produce a crater with a radius of 608 feet and a depth of 323 feet (9). Fifty-eight percent of the crater mass or 4.8 million tons of desert alluvium were ejected from the crater during the detonation and distributed somewhat symmetrically around the ground zero point to a distance of 6000-7000 feet (1). 

Nordyke, M. D., An Analysis of Cratering Data from Desert Alluvium, J. Geophysical Research 67 (5), May 1962. 

Walker, T.R., Waugh, B. Crone, A.J. (1978) Diagenesis in first-cycle desert alluvium of Cenozoic age, southwestern United States and northwestern Mexico. Geol. Soc. Am. Bull., 89, 19-32. 

The ejecta or earth materials deposited on the desert surface around the crater consisted of large rock missiles on long trajectories, alluvium lifted and ejected in mass (bulk ejecta), and materials which remained airborne for longer times (missile ejecta). Fine particles remaining in the cloud were transported greater distances from the crater and constitute close-in and long range fallout. 

CALICHE (Nitrate). The gravel, rock. soil, or alluvium cemented with soluble salts of sodium in the nitrate deposits of the Atacama Desert of northern Chile and Peru. The material contains from 14 to 25% sodium nitrate, 2 to 3% potassium nitrate, and up to I i sodium iodaic. plus some sodium chloride, sulfate, and borate. At one time, this was an important natural fertilizer. 

Entisol Nonsense syllable ent, from recent Negligible differentiation of horizons in alluvium, frozen ground, desert sand, and so on, in all climates... 

Basalt, with desert varnish Same basalt, without desert varnish Coarse granite alluvium (0 1 mm)... 

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