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Scanning Electron Microscopic Analysis Of Rock Varnish Chemistry For Cation-Ratio Dating: An Examination Of Electron Beam Penetration Depths, Steven L. Reneau, Roland C. Hagan, Charles D. Harrington, Robert Raymond Jr.

Scanning Microscopy

Rock varnish is a microns-thick manganese- and iron-rich coating that forms on exposed rock surfaces in arid and semi-arid environments, and empirical correlations of the varnish cation ratio (K+Ca):Ti with age have been used to estimate ages of geomorphic surfaces. One method of obtaining varnish chemistry for cation-ratio dating involves scanning electron microscope (SEM) energy dispersive x-ray (EDX) analysis of natural varnish surfaces. The chemical analyses of rock varnish with SEM/EDX utilize a sequence of accelerating voltages to vary penetration depths into the sample. Using elemental x-ray maps of natural varnish surfaces obtained by SEM/EDX analysis, penetration into the substrate …