Monday, January 20, 2020
Soil Formation Under Desert Pavements Essay -- Geology Topography Pape
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 shrink and swell clay characteristics were at one time believed to be the main factors in the formation of desert pavements (Mabbutt, 1977). However, more recent research has shown that desert pavements are born and maintained at the surface, and that the soil below them is mainly eolian in origin . Slow accretion of eolian dust below the pavement is a process that eventually develops cumulate horizons. Eolian dust in environments where pavements often develop is rich in carbonate salts and clays due to the fact it often originates from nearby playa lake evaporate basins (McFadden et. al., 1987). Soils that form below the pavements over time develop calcic horizons and clay rich structure due to the influx of these eolian fines through the pavement surface. In turn the development of mature or plugged calcic horizons effects the form of the pavement surface because it alters the water drainage infiltration rate and causes pavements to decline. Desert Pavements Desert pavements form in several di... ...cFadden, Leslie D., 1988, Climatic Influences on rates and processes of soil development in Quaternary deposits of Southern California: Geological Society of America Special Paper 216, p. 153-175 Mc Fadden, L. D., Wells, S. G., and Jercinovich, M. J., 1987, Influence of eolian and pedogenic processes on the origin and evolution of desert pavements: Geology, v.15, p. 504-508. Ritter, Process Geomorphology Wells, Stephen G., Dohrenwend, John C., McFadden, Leslie D., Turrin, Brent D., and Mahrer, Kenneth D., 1985, Late Cenezoic evolution on Lava Flow surfaces of the Cima volcanic field, Mojave Desert, California: Geological Society of America Bulletin, v. 96, p. 1518-1529. Wells, Stephen. G., and Mc Fadden, Leslie D., 1995, Cosmogenic 3He surface-exposure dating of stone pavements: Implications for landscape evolution in deserts: Geology, v. 23, p. 613-16.