Physical Sciences and Mathematics Commons^™

Phenomena Relating To Charge In Insulators: Macroscopic Effects And Microscopic Causes, Jacques Cazaux, Claude Le Gressus

Scanning Microscopy

Conservation of current under steady-state conditions makes it possible to determine the sign of charges trapped in an insulator subjected to ionizing radiation. The maximum value of the surface potential can thus be estimated.

On the basis of a given trapped charge distribution, the pattern of the electrical field and of the potential can thus be established, and the influence of the shape of the sample and its environment can be clearly shown. Change of trapped charges with time (at the start and after irradiation) is then examined. Finally, the microscopic causes of trapping of charge is suggested by analogy …

Elemental Relationships In Rock Varnish As Seen With Scanning Electron Microscopy And Energy Dispersive X-Ray Elemental Line Profiling, Robert Raymond Jr., Steven L. Reneau, Charles D. Harrington

Scanning Microscopy

The heterogeneous nature of rock varnish requires a thorough understanding of elemental and mineralogic compositions before chemical variability of rock varnish may be confidently related to varnish age or to past geochemical environments. Elemental relationships in rock varnish were examined using scanning electron microscopy in conjunction with an elemental line profiling routine using semi-quantitative, energy-dispersive x-ray analysis. Results of our analyses suggest: 1) variations in cation concentrations used in varnish cation-ratio dating relate more specifically to variations in detritus concentration within the varnish than to element mobility as defined by weathering indices; 2) Mn:Fe ratios may be a poor indicator …

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 …

Barium Concentration In Rock Varnish: Implications For Calibrated Rock Varnish Dating Curves, C. D. Harrington, D. J. Krier, R. Raymond Jr., S. L. Reneau

Scanning Microscopy

Cation-ratio dating of rock varnish is a recently developed technique for obtaining surface exposure ages of a wide variety of geomorphic surfaces. As originally proposed, the technique utilizes a ratio among minor cations [(K+Ca)/Ti] in rock varnish. Although this varnish cation ratio is related to the Ti concentration, it can also be affected by the presence of Ba that may be partially included in the analyzed concentration of Ti. Barium is a minor constituent found in virtually all rock varnishes sampled from the Lake Mead area, Las Vegas Valley, and the Crater Flat region of southern Nevada. Barium is heterogeneously …