Desert varnish: evidence for cyclic deposition of manganese

@article{Perry1978DesertVE,
  title={Desert varnish: evidence for cyclic deposition of manganese},
  author={Randall S. Perry and John B. Adams},
  journal={Nature},
  year={1978},
  volume={276},
  pages={489-491}
}
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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A note on the characteristics and possible origins of desert varnishes from southeast Morocco
Two substrate-controlled varnish types were identified from arid southeast Morocco: (1) patchy varnish interspersed with ‘silica glaze’ on silicified limestone and (2) a complete varnish cover on
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References

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Desert varnish forms a dark coating up to 0.10 mm thick on the exposed surfaces of many stones and outcrops in southern California deserts. Wet chemical analyses were made of varnish, the underlying
Desert varnish and marine ferromanganese oxide nodules: congeneric phenomena
BLACK, hydrated ferromanganese oxide (FMO) concretions of microscopic to macroscopic size and complex mineralogy cover ocean floors all over the world at depths of up to 8 km (ref. 1). These
Desert Varnish: An Electron Probe Study
Desert varnish samples from Deep Springs Valley and Death Valley in California were studied with the use of the electron microprobe. Varnish can be interpreted as having two layers, an inner
Geochemistry of Ferromanganese Oxide Concretions and Associated Deposits in Lake Ontario
A large deposit of ferromanganese oxide coated sands and scattered manganese nodules occurs in the northern portion of Lake Ontario. The Mn and Fe contents of the concretions are similar to those in
Über den Einfluß der Mikroflora auf die exogene Dynamik (Verwitterung und Krustenbildung)
ZusammenfassungGeomikrobiologische Untersuchungen können zur Klärung vieler ungelöster Fragen des exogenen Kreislaufes der Elemente beitragen. Mikrobiologische Verwitterung und Krustenbildung finden
Pre-Altithermal Archaeology in the Sierra Pinacate, Sonora, Mexico
The 600 square mile volcanic area of the Sierra Pinacate, in extreme northwestern Sonora, Mexico, comprises a unique geologic and ecologic enclave in which archaeological remains have been
Desert Varnish: The Importance of Clay Minerals
Desert varnish has been characterized by infrared spectroscopy, x-ray diffraction, and electron microscopy. It is a distinct morphological entity having an abrupt boundary with the underlying rock.