THE ROLE OF QUARTZ LUMINESCENCE IN FINGERPRINTING FIRE AND CRITICAL ZONE PROCESSES

Quartz optically stimulated luminescence (OSL) dating has become a mainstay in Quaternary research, with an applicable age-range covering the last 200-kyr (longer in some cases) and well-known applications spanning the fields paleoseismology, geomorphology, and archaeology. However, what is lesser known is that the unique luminescence properties of quartz, can be used as a valuable proxy for exposure to surface processes and duration of time spent within the critical zone.

Luminescence sensitivity of quartz, recorded as the brightness of the OSL signal generated per applied lab dose of radiation, has been shown to vary between geologic terrains and rock types, providing a promising tool for provenance analysis. However, observations also suggest that quartz sensitivity may be enhanced by sediment-transport. Although the mechanisms that generate quartz sensitization are not fully understood, data suggesting that longer residence time within the critical zone leads to enhanced quartz sensitivity, likely due to greater cumulative exposure of grains to sunlight and fire at the Earth’s surface. The repeated exposure to optical, mechanical, and thermal energy can release trapped charge from strongly held traps (defects) within the crystal lattice, enhancing luminescence sensitivity. Examples of linkages between quartz luminescence sensitivity and climate-mediated weathering, tectonic-driven erosion rates, exposure to fire and duration within the critical zone are presented here and factors that encode quartz OSL sensitivity.