Dr. Chad Pritchard
Folded and altered quartzite along Interstate 90 and the Palouse to Cascades Trail out of Rosalia, WA preserves a record of the region’s tectonic past. The working hypothesis is that the sandstone is Cambrian (roughly 500 million years old) and was metamorphosed and deformed during the Sevier orogeny (roughly 150 to 50 million years ago), and then uplifted about 50 million years ago. The first step to address the hypothesis is to determine the age of the rocks using detrital zircon U/Pb analyses. The second step is for a detailed field study to identify relationships between metamorphic grades and geologic structures. For comparison samples from the nearby Steptoe Butte were also analyzed, which is likely Cambrian (roughly 500 million years ago) based on an abstract with un-published results by Ellis and others (2004). From this study we hope to help decipher the older geological past of our area, since so much of our regional geology is dominated by younger 16-million-year-old basalt and 16,000-year-old mega flood deposits.
Morton, Travis A. and Pritchard, Chad, "Detrital zircon ages in heavily folded quartzite compared to Steptoe Butte" (2022). 2022 Symposium. 21.
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