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Distribution of desert varnish in ArizonaDesert varnish is the dark coat of clay and ferromanganese oxides developed on exposed rock surfaces in arid regions. It forms from the accretion of material from windblown dust. The distribution of desert varnish was mapped in Arizona. It was discovered that desert varnish could be mapped on a regional scale. Well developed desert varnish is common on stable rock surfaces in areas having alkaline soils and less than about 25 cm of annual precipitation. Rock surfaces in areas having more than 40 cm of annual precipitation are generally devoid of desert varnish. An experiment was conducted with varnished desert pavement stone. The stones were broken in half and half was set on a roof in central Illinois from April until October. Removed from the alkaline desert environment, it only took seven months for the varnish to develop an eroded appearance. This experiment graphically illustrates the dependency of desert varnish on alkalinity. In this context, the zones of eroded desert varnish in Arizona indicate that the area of active desert varnish formation has fluctuated, expanding in drier times and contracting/eroding in wetter times.
Document ID
19890016974
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Elvidge, Christopher D. (Desert Research Inst. Reno, NV, United States)
Date Acquired
September 6, 2013
Publication Date
March 1, 1989
Publication Information
Publication: NASA, Ames Research Center, Exobiology and Future Mars Missions
Subject Category
Geophysics
Accession Number
89N26345
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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