Assessing the potential for luminescence dating in the Mojave Desert, California
A reliable, widely applicable geochronological tool is an imperative part of neotectonic studies. While there are several geochronological techniques available for Quaternary research, each method has its limitations. Luminescence dating has huge potential for these kinds of studies, as it relies on commonly occurring minerals (namely quartz and K-feldspar), directly dates the event of interest, can be applied over a wide range of timescales, and gives ages without any complex calibration required.
While optically stimulated luminescence (OSL) dating of quartz and infrared stimulated luminescence (IRSL) dating of K-feldspar work well in many regions, these techniques have proven problematic for many OSL users and dating specialists in southern California. Issues of low sensitivity and low (dim) signal intensity often yield inconsistent and questionable results. It is the aim of this study to develop an improved methodology for luminescence dating in this region.
From the El Paso Peaks trench site on the central Garlock fault, several samples were collected for luminescence dating. Conventional quartz OSL protocols did not yield accurate age estimates. Various K-feldspar IRSL protocols were tested in this study, while new techniques were developed and assessed. Experimentation with two novel procedures, the selective SAR48-12 and SACoR approaches, demonstrate great potential for innovative new ways to deal with problematic samples. The novel K-feldspar isothermal thermoluminescence (ITL) approach gives encouraging results, although further research is warranted to determine how robust and widely applicable the technique is. Because of the pervasive problem of incomplete bleaching in the region, single-grain K-feldspar IRSL measurements may be the best technique for isolating well bleached grains and determining precise and accurate age estimates.