Examining the relationship between portable luminescence reader measurements and depositional ages of paleowetland sediments, Las Vegas Valley, Nevada

Portable luminescence readers are exciting new tools that have the potential to rapidly determine the age structure of late Quaternary stratigraphic columns. This is important because high-resolution age profiling can reveal details about the temporal dynamics of climate cause and ecosystem effect, often while researchers are still in the field. In this paper, we compare new portable luminescence reader measurements of total photon counts with a suite of robust, highly resolved ages from middle to late Pleistocene-age paleowetland deposits in the Las Vegas Valley of southern Nevada. Our results show that total photon counts correlate with age, with a quadratic equation providing the best fit to the data. Significant scatter is present in the data, which is likely the result of dose rate variations, multiple sediment sources, and transport mechanisms that include both eolian and fluvial processes. The observed scatter can be reduced significantly using a simple pretreatment procedure involving a 250 mu m sieve and neodymium hand magnet to normalize particle sizes and remove magnetic grains. Following this treatment, age estimates based on the reader measurements have an average error of 30 +/- 18% when compared against known ages. These findings confirm that portable reader measurements scale with age in paleowetland deposits, allowing its use in establishing rapid, albeit approximate, chronologies for these deposits throughout the American Southwest.