EXPLORING LUMINESCENCE-BASED METHODS FOR DATING PHREATOMAGMATIC ERUPTIONS: A CASE STUDY FROM SODA LAKE, NV

Soda Lake is a basaltic Holocene maar located in northwestern Nevada, USA. A maximum age of ~13,000 years is currently the best age constraint for the eruption given that the eruptive deposits cover lake sediments of pluvial Lake Lahontan, though some workers have proposed that the eruption must have occurred less than ~6,000 years ago owing to the absence of Holocene shorelines on the outside of the crater. A more recent estimate based on radiocarbon dating of pollen from cored lake sediments suggests that the eruption may have occurred up to 14,700 years ago but likely not less than 7,000 years ago. In this work, we apply optically stimulated luminescence (OSL) dating to feldspar and quartz of xenocrystic origin in attempt to define the eruption age of Soda Lake and resolve conflicting age estimates. OSL dating is geochronological technique that can be used to determine the time elapsed since quartz or feldspar grains were exposed to temperatures in excess of 400 °C. Our fading corrected IR₅₀ and non-fading corrected post-IRIR₂₂₅ ages from xenocrystic feldspar are statistically indistinguishable, yielding an average age of ~5,500 years for the Soda Lake maar eruption. The quartz OSL signal was dominated by medium and slow components leading to significant age underestimation relative to the feldspar extracts. Further work is underway to attempt to isolate a stable signal from the xenocrystic quartz at Soda Lake. Luminescence dating is one of few direct dating methods that can be applied to volcanic materials of Holocene age and should be considered, particularly where the application of other radiometric dating techniques are not a viable option.