Reflectance Spectra of Obsidians for Age Determination

The framework of this research is the use of spectra from Holocene obsidian lava surfaces for age determination. The study comprises spectroscopy, X-ray diffraction (XRD) methods. In addition, optically stimulated luminescence (OSL) technique to obtain absolute age dates of rock samples has been done. Weathering (in the form of hydration) acts on the rock surfaces owing to the reflectance variation. The reflectance spectra of the rock samples from individual obsidian flows correlates with their relative/absolute ages to some extent. A similar relationship was realized for their per channel emittance. In addition, the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image of the lava flows in the Tullu Moje and Corbetti volcanic complexes in the Main Ethiopian Rift (MER) show an increase in apparent reflectance with increasing age. The conclusions of this investigation revealed that there is an indication that the reflectance spectra (brightness) from obsidians can be used for dating of lava flows.