BRINGING THE ROCKY MOUNTAIN REGION TO LIGHT: A SUMMARY OF THE USGS LUMINESCENCE GEOCHRONOLOGY LAB SHARED PROJECTS, RESEARCH, AND NEW UTILITIES OF THE TECHNIQUE IN FEDERAL AND STATE COLLABORATIONS

Luminescence dating can be applied to sand- and silt-sized particles in a variety of Quaternary deposits found in the Rocky Mountains and intermountain west. Luminescence provides an age estimate of the last time quartz and feldspar minerals were exposed to light or heat. While it is complimentary to radiocarbon and cosmogenic nuclide dating techniques (i.e. to measure the timing of deposition or cultural occupation), it requires no organic material or production rate, and it can produce ages beyond the limit of radiocarbon detection and more precisely than cosmogenic nuclides. The typical optically stimulated luminescence (OSL) date range for quartz is ~100,000-200,000 years while infrared stimulated luminescence (IRSL) on potassium rich feldspars measures ages as old as 200,000-400,000 years. The variability in maximum age ranges is a function of the geological sources of sediment, natural dose rate and the saturation limit of the mineral sampled. Publications and applications of luminescence dating to geomorphic and archaeologic settings has grown exponentially in the past decade worldwide, with a notable acceleration of product enhancement within the last decade.

We will present a review of the past applications of luminescence dating in the Rocky Mountain region, discuss geochronological entries in databases (i.e. the Utah Geological Survey and USGS), and evaluate ways in which luminescence dating could be utilized more frequently in natural hazards assessments with state and federal partners. OSL has been particularly useful in allowing for rapid sample analyses via a portable OSL reader for paleoseismic trench work. We will present some exciting new applications for this instrument. Practical examples will be provided in this presentation with highlights regarding what to target and avoid when collecting various sample components for OSL/IRSL dating. In addition, we will provide examples of best sampling practices across a variety of geomorphic settings and elaborate on innovative applications of OSL to cultural materials (i.e. pottery).