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1 Department of Geological Sciences and Quaternary Research Center, University of Washington, Box 351310, Seattle, Washington 98195
Cosmogenic 36Cl/Cl ratios measured from glacially eroded bedrock provide the first quantitative constraints on the magnitude, rate, and spatial distribution of glacial erosion over the last glacial cycle. Of 23 36Cl/Cl ratios, 8 yield exposure ages that predate the well-constrained deglaciation of the Puget Lowland, Washington, and are inferred to result from 36Cl inherited from prior exposure during the last interglaciation where ice did not erode enough rock (
1.80–2.95 m) to reset 36Cl/Cl ratios to background levels. Surfaces possessing inherited 36Cl evidently were abraded only 0.25–1.06 m, corresponding to abrasion rates of 0.09–0.35 mm 
yr–1. These results indicate that in the absence of glacial quarrying, the Cordilleran ice sheet may have abraded as little as 1–2 m of bedrock near its equilibrium-line altitude over the last glacial cycle, equating to only tens of meters over the entire Quaternary.
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