OPTICAL DATING OF EOLIAN LANDFORMS USING QUARTZ IN BRITISH COLUMBIA AND WESTERN ALBERTA, CANADA – CHALLENGES AND OPPORTUNITIES

The timing and character of post-glacial climate-driven landscape change in western Canada is largely understood by observing changes in eolian landforms. In many cases a paucity of material suitable for radiocarbon dating has required the use of optical dating (often referred to as optically stimulated luminescence (OSL) dating) to put the nature of landscape change in a secure temporal context. In general, the two most common minerals used for optical dating are quartz and feldspar. Quartz is preferred because of its abundance in sedimentary landforms, and because its luminescence signal (‘clock’) is reset much more easily by sunlight than that for feldspar. Moreover, the appropriate luminescence signal from quartz is stable over the required time period, whereas that from feldspar fades. This so-called anomalous fading requires, where possible, additional experiments to correct or circumvent it, which adds uncertainty to calculated ages. However, the usefulness of quartz as a chronometer in recently eroded landscapes is complicated because young sedimentary quartz often has not developed the luminescence sensitivity required to make it useful for dating. This is problematic in recently-glaciated regions dominated by igneous rock, such as much of British Columbia. There is, nevertheless, hope in regions where bedrock includes sedimentary rock that has undergone little diagenesis. In this presentation we will review some of the luminescence signals observed in sedimentary quartz from British Columbia and western Alberta and discuss their utility in dating the eolian landforms in which they are found