Desert varnish: evidence for cyclic deposition of manganese

  title={Desert varnish: evidence for cyclic deposition of manganese},
  author={Randall S. Perry and John B. Adams},
WE have found evidence that desert-varnish coatings on rocks in the western US consist of micron-scale alternating dark and light layers that differ in manganese and iron content. We report here the first quantitative electron-microprobe analyses of desert varnish, that also show the chemical variations in these layers. In the field and laboratory we obtained new evidence that varnish covers a fresh substrate by nucleation of micron-sized patches that grow and coalesce. 
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  • R. Dorn
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