Soil Formation Under Desert Pavements Essays

2162 Words 9 Pages
Soil Formation Under Desert Pavements

Desert pavements are common landforms in arid regions. They consist of flat or sloping surfaces where stones are closely packed angular or rounded, and generally exhibit low relief (Mabbutt, 1977). Pavements tend to form on both alluvial fan toposequences and on weathering volcanic flow fields in arid regions. Soils are often found under desert pavements and they play an important role in the evolution of pavements (McFadden et. al., 1987). In the past there have been several theories as to the formation pavements and soil development beneath them. Deflation, or the erosion of finer grained particles from a surface, stone concentration by wash erosion and upward displacement of stone due to
…show more content…
Desert pavements are frequently covered with a surface deposit known as desert varnish. Desert varnish is a thin dark coating of iron oxide and manganese oxide and silica that occurs after prolonged exposure on a surface (Bates and Jackson, 1987). Degree of varnish development can be used as a relative age determinant when the level of darkening of surfaces of different ages is compared. Varnish may also be used to yield absolute ages when cosmogenic exposure dating techniques are used.

Stone pavements form on lava flows such as the basalts of the Cima volcanic field in the Mohave Desert, California (McFadden et. al., 1987). There are two main processes that contribute to the origin and evolution of these pavements, the deposition and peodogenic change of an eolian mantle and mechanical weathering of rocks from topographic highs to lead to the development of a rubble zone. This rubble zone eventually becomes the desert pavement. Therefore, the clasts and adjoining bedrock topographic highs are relatively made of the same lithology and are of the same age (Wells et. al., 1995). The pavement often resembles a puzzle, with pieces that tightly interlock. Under this stone pavement a relatively gravel free eolian mantle accretes that develops pedogenic features.

Alluvial fans are flat to slightly sloping areas covered in loose rock in a fan shape usually deposited where a stream flows from a mountain valley into a

Related Documents