Rock varnish

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Abstract

Firstly, a hypothesis of rock varnish formation by certain bacteria is discussed, resulting over thousands of years in a thin coating of clay, cemented to rocks by Mn and Fe. The interpretation of landscape development is examined by describing dating techniques such as radiocarbon dating; dust fallout by energy-dispersive X-ray analysis of the three-dimensional structure of the varnish; geochemical signals such as heavy metal pollutants; and differentiation of C3 and C4 plants and hence climatic humidity by microscopic analysis of organic debris. The example of an alluvial fan in Death Valley, Arizona, over the last 50 000 yr is used to demonstrate palaeoenvironmental reconstruction, and hence the stages in its development. The article is concluded by applications in archaeology for dating of rock engravings. -J.W.Cooper

Original languageEnglish (US)
Pages (from-to)542-553
Number of pages12
JournalAmerican Scientist
Volume79
Issue number6
StatePublished - Jan 1 1991

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    Dorn, R. (1991). Rock varnish. American Scientist, 79(6), 542-553.