Uranium-series and luminescence dating of volcanic lithic artefacts

U-series dating was used to determine the growth rate of a feldspar-to-clay weathering rind in a mid-Holocene Cascade-Olcott tradition andesite core, and luminescence dating (last exposure to sunlight) was used to date fine-grained feldspars scraped from the surfaces of similar buried artefacts from a ¹⁴C-sediment-dated archaeological site (45K1464) on the wet western slope of the Cascade Mountains of Washington. For U-series dating, we measured ²²⁶Ra excess (²²⁶Ra excess = ²²⁶Ra - ²³⁰Th) in five stratigraphic depth controlled rind scrapings. ²³⁸U, ²³²Th and ²³⁰Th were counted by alpha spectrometry, and ²²⁶Ra and ²¹⁰Pb were counted by gamma spectrometry on each sub-sample.