TESTING AGE PREDICTIONS MADE WITH PORTABLE OSL MEASUREMENTS IN SOUTHERN NEVADA

Luminescence is a widely used geochronologic tool that measures depositional ages. New portable luminescence readers now allow for the rapid assessment of the luminescence characteristics of deposits. One potential application of portable OSL readers is to generate predictions of depositional age. Here, we present a comparison between portable OSL measurement and known depositional ages for field sites in southern Nevada. We find a correlation between portable OSL measurement and depositional age. The correlation improves greatly when samples are sieved to below the 250-micron grain size and have magnetic grains removed by a handheld neodymium magnet. We find that the relationship between depositional age and portable OSL measurement can be adequately described with a second order polynomial fit to the data. This relationship can be found for both OSL and IRSL. Measurements made on unsieved samples have significant scatter that obscure the correlation with age and portable OSL measurement. Some samples are strong outliers despite treatment and appears to be due to contamination by apatite. The relationship between age and portable OSL measurement suggests that we can make age predictions from the fitted polynomial for lithologically similar units in the region near our field sites. To see if our polynomial regression can produce robust age predictions, we compare portable OSL measurements on new samples and then determine their age using standard geochronology such as luminescence dating and/or radiocarbon. We present preliminary results on this comparison and we find notable success. Some samples produce incorrect age predictions, which is likely due to apatite contamination. Further data collection will help provide a clear picture of portable OSL age prediction for our field sites.