FTIR and SEM characterization of desert varnished rocks
EMSL Project ID
14791
Abstract
We intend to characterize the spectral, polarization, and microscopic morphology of desert varnished rock samples using FTIR polarization and SEM analyses. This work supports the efforts of the PI to characterize the trafficability of desert terrains through the identification of desert pavement landforms. Previous work by the PI has shown that varnishes strongly polarize at visible wavelengths (whereas the substrate does not), but are generally sufficiently think to be partially transparent in the thermal infrared (TIR) so that the substrate is detected. Thus, if varnishes polarize in the TIR as well as the visible, it may be possible to use the degree of polarization in the TIR for characterizing the thickness of desert varnishes. Varnish that is optically thick in the TIR (~ 100microns thick or greater) may polarize light at TIR wavelengths more than thinner, partially transparent varnish coatings. Thus, polarization in the TIR may offer a means of estimating varnish thickness, and thus surface maturity. However, the degree of polarization is also dependent on the scattering properties of the material which is dependent on the sizes and orientations of grains within the varnish. Thus, even though varnish polarizes strongly at visible wavelengths, the structure of the varnish may be such that its polarization properties are intrinsically different in the TIR, even if optically thick. In order to fully understand any observed (or not observed) TIR polarization, the morphology of the sample at a microscopic scale needs to be determined. We intend to use SEM for this.
Project Details
Project type
Exploratory Research
Start Date
2005-04-15
End Date
2006-03-30
Status
Closed
Released Data Link
Team
Principal Investigator