Some Properties and Age of Volcanic Ash in Glacier Bay National Monument

Volcanic ash occurs in a 12-m thick section of gravels, silt and sand, exposed on both sides of Granite Canyon in the eastern part of the Monument. C-14 dates on wood from nearby marine deposits indicate an age for the ash of approx 11,000 BP. Mount Edgecumbe near Sitka may have been the source. Results of granulometric, petrographic and chemical analyses are reported. The ash was deposited in a near-shore marine environment as part of the Forest Creek Formation