USING QUARTZ LUMINESCENCE OF SAND TEMPER FROM ARCHAEOLOGICAL POTTERY TO INFER THE INTENSITY OF PAST WILDFIRES IN THE SOUTHWESTERN US

The size and frequency of wildfires have increased recently, impacting ecosystems, communities, and human health. My research uses heat-sensitive luminescence signals of quartz sand temper within archaeological pottery to record past wildfire intensity (heat exposure and duration) which can reset its archaeological age. Pottery from surface sites in dry ponderosa and pinyon-juniper woodlands in New Mexico and Arizona were collected from different fire contexts (no fire exposure, historical fires, prescribed burns, and modern wildfires). The pottery samples have an established archaeological age, using single-grain optically stimulated luminescence dating we can determine if the sherd has been exposure to intense heat from a wildfire. Single-grain resolution will allow us to determine the proportion of the grains that were reset in case of non-complete thermal resetting.

The luminescence signal of individual quartz grains in pottery temper from each fire context will be used to test my hypothesis that recent fire intensity (heat and duration) is greater than past natural wildfire conditions prior to Euro-American Forest management and anthropogenic climate change. Limited observations support my hypothesis, pottery exposed to recent high-intensity fire has produced modern (reset) luminescence signals, while ceramics exposed to centuries of historical fires retain their archaeological age. Such results may indicate that modern fires are burning hotter and longer due to decades of fuel accumulation in response to forest management practices of suppression/ prevention, and drier, more flammable fuels and longer burn seasons due to climate change. The approach and results of this study could provide a unique proxy of past wildfire conditions that can be used to test the importance of fuel conditions and climate change on fire intensity.